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The Effect of Manipulation in Energy Allowance During the Rearing Period of Heifers on Hormone Concentrations and Milk Production in First Lactation Cows
Abstract
Fifteen Holstein heifers that were 175 +/- 4.0 d old and at BW of 175 +/- 4.9 kg were used to determine the effect of three feeding regimens from 6 to 12 mo of age on growth, blood concentration of several hormones, and milk production during first lactation. The feeding regimens consisted of two periods, the first lasting for 4 mo and the other for the subsequent 2 mo. For group A (restricted) heifers, the diet during period 1 was restricted to 85% of NRC (1988) recommendations (a daily BW gain of .7 kg); during period 2, a high energy, high protein diet was provided for ad libitum intake. Group B (control) heifers received a diet that corresponded to 100 and 90% of the NRC (1988) recommendations in periods 1 and 2, respectively. Group C (ad libitum) intake heifers received a high energy, high protein diet throughout both periods. Daily BW gains of heifers of groups A, B, and C were, respectively, .625, .768, and 1.100 kg for period 1 and 1.162, .705, and .797 kg for period 2. The different feeding regimens influenced the age at which the heifers achieved puberty but did not affect BW at puberty. Milk production during 250 d of lactation was 7056, 6070, and 5975 kg for groups A, B, and C, respectively. A statistical model that included serum derived mitogenic activity and serum prolactin of period 2 accounted for 63% of the difference in milk production at first lactation.
... Radcliff et al. (1997) (Sejrsen und Foldager 1992). Außerdem soll sich die präpubertäre Prägungsphase, in der die Fütterungsintensität die spätere Milchleistung beeinflussen kann, auf einen Abschnitt beschränken, in dem die Tiere 90 bis 300 kg wiegen (Foldager und Sejrsen 1983;Peri et al. 1993;Andreae und Müller 1997;Macdonald et al. 2005). ...
... Gleichermaßen umfasst sie einen Teil der präpubertären Entwicklung. Eine intensive Fütterung in dieser Phase kann sich nachteilig auf die spätere Milchleistung auswirken (Foldager und Sejrsen 1983;Peri et al. 1993;Andreae und Müller 1997;Macdonald et al. 2005 (Bines und Hart 1982;Li et al. 2007). Propionat wird aus leicht verdaulichen Kohlenhydraten synthetisiert, deren Anteil in der energetisch hoch konzentrierten Ration besonders groß war (Vestergaard et al. 1993;Yambayamba et al. 1996 (Steiner 1987;Verde und Trenkle 1987;Hall et al. 1995;Sakurai et al. 2004). ...
... Es ist jedoch nicht auszuschließen, dass bei einer höheren Tierzahl (nur 11 Zwillingspaare standen bis zum 305-Laktationstag zu Verfügung) die Signifikanzschwelle unterschritten worden wäre. Ergebnisse aus anderen Arbeiten sprechen dafür, dass eine moderate Fütterung von Jungtieren die Milchleistung günstig beeinflussen kann(Peri et al. 1993; Lammers et al. 1999b;Sejrsen et al. 2000;Radcliff et al. 2000). Anhand der vorliegenden Untersuchungen könnte dies vor allem mit geringeren Belastungen des Stoffwechsels und einer höheren Futteraufnahme in Verbindung stehen, wobei die individuelle genetische Konstellation für die Leistungsreaktion während der Laktation bedeutsam ist. ...
In einem Fütterungsversuch mit 15 weiblichen, genetisch identischen Zwillingspaaren wurde der anhaltende Effekt energetisch unterschiedlich konzentrierter Futterrationen auf Körper- und Blutmerkmale zwischen dem vierten und 21. Lebensmonat erfasst. Die gleichen Merkmale wurden an den Tieren auch während der Laktation erhoben, als die Tiere einheitlich gefüttert wurden. Zusätzlich wurde die Milchleistung untersucht. Während der Aufzucht wurden Körpergewicht, tägliche Gewichtszunahme, Rückenfettdicke und Widerristhöhe von der Fütterungsintensität signifikant beeinflusst. Körpergewicht und Rückenfettdicke zeigten vom siebenten bis 15. Lebensmonat die größten Unterschiede zwischen den Fütterungsgruppen. Im Gegensatz zum Körpergewicht, wurde der Fettansatz bis zum 21. Lebensmonat kaum gebremst. Für die Serumkonzentrationen von Insulin, Glukose und beta-Hydroybuttersäure und die Erythrozytenindizes MCV und MCH konnte ein signifikanter Fütterungseinfluss während der gesamten Aufzuchtphase nachgewiesen werden. Kortisol, Kreatinin, ASAT, GGT, GLDH, MCHC, Leukozytenzahl, Thrombozytenzahl reagierten auf den Fütterungsstimulus nur innerhalb bestimmter Altersabschnitte. Bis zum neunten Monat differierte der Insulinspiegel zwischen den Fütterungsgruppen kaum, ab dem 10. Lebensmonat aber sehr deutlich. Es kann daher ausgeschlossen werden, dass der Insulinspiegel im präpubertären Abschnitt die Entwicklung der späteren Milchleistung beeinflusste. Nach dem Abkalben war die intensiv gefütterte Gruppe stärkeren metabolischen Belastungen ausgesetzt und hatte eine geringere Milchleistung als die moderat gefütterte Gruppe. Offensichtlich wurde der Stoffwechsel durch die vorangegangene Fütterung geprägt, da der Fettansatz in der Intensivgruppe bei gleicher Fütterung früher einsetzte und auch intensiver erfolgte. Einige Kennwerte beim Jungtier korrelierten signifikant mit der späteren Milchleistung. Altersabhängige Veränderungen der Korrelationskoeffizienten weisen auf unterschiedlich sensible Phasen für die Prägung der späteren Milchleistung hin.
... With regard to the effect of Lwt at first breeding on reproduction and animal longevity, both Archbold et al. (2012) and McNaughton and Lopdell (2013) reported an effect of heifer Lwt at 15 months on time to pregnancy; however, at least in the case of Archbold et al. (2012), this effect reflected the number of heifers that had not attained puberty at the onset of the seasonal breeding season and was not an effect of heifer Lwt per se. Of course, as puberty is influenced by Lwt (Foldager et al. 1988;Peri et al. 1993;Niezen et al. 1996), it must be acknowledged that too low a Lwt gain pre-puberty, which results in heifers not having reached puberty by planned start of breeding, will delay breeding and first calving, and reduce the likelihood of pregnancy during the first lactation; this was reflected in a lower longevity in first and second lactation in the lowest heifer-Lwt quartile (Archbold et al. 2012). Nonetheless, in their dataset, as long as the heifers were at a sufficient Lwt to attain puberty before breeding, time to a successful pregnancy and longevity of the animal did not vary. ...
... Ford and Park 2001). Others have confirmed the presence of compensatory growth in stature in dairy heifers, when 2 months of ad libitum feeding followed 4 months of a restricted allowance (Peri et al. 1993;Barash et al. 1994). However, the effect on milk production was not consistent; Barash et al. (1994) reported no effect of rearing method on milk production, while Peri et al. (1993) identified a 16% increase in milk yield and a 9% and 2% increases in milk fat and protein yields, respectively. ...
... Others have confirmed the presence of compensatory growth in stature in dairy heifers, when 2 months of ad libitum feeding followed 4 months of a restricted allowance (Peri et al. 1993;Barash et al. 1994). However, the effect on milk production was not consistent; Barash et al. (1994) reported no effect of rearing method on milk production, while Peri et al. (1993) identified a 16% increase in milk yield and a 9% and 2% increases in milk fat and protein yields, respectively. Similarly, Ford and Park (2001) reported 1.5-fold increase in growth efficiency (Lwt gain/ DM intake) and 21% and 15% increases in firstand secondlactation yield, respectively, in animals subjected to repeating periods of restriction and re-alimentation; however, there were only four and three cows per treatment, respectively, in each of these lactations, and the milk-production results should be viewed cautiously. ...
Dairy heifer growth and liveweight at first calving are regarded as important management variables affecting profitability and animal welfare. However, the appropriateness of heifer growth rate targets for different farming systems is not clear. Retrospective assessments of the association between heifer liveweight and subsequent productivity indicate significant benefits in milk production and, even, reproduction from increasing liveweight at breeding and first calving. However, prospective interventionist experiments do not concur, with very variable effects of liveweight at breeding on milk production and with only limited evidence of a positive effect of first-calving liveweight on first-lactation milk yield. In addition, any benefit in the first lactation is not evident in subsequent lactations in the limited number of long-term studies reported. Pre-weaning nutrition and average daily weight gain are areas of increasing interest, with lifelong increases in milk production resulting from accelerated growth rates during the first 8 weeks of life, indicating a possible significant return from a short-term investment. This could be one reason for the inconsistent effects of heifer liveweight at breeding and first lactation on milk production. Although the effect of pre-weaning average daily gain on heifer liveweight is short-lived, a recent meta-analysis indicated that pre-weaning average daily gain explains 22% of the variation in first-lactation milk production. Whether these differences in animal physiology have relevance in grazing systems, wherein heifers and cows do not consume sufficient nutrients to reach their potential, requires investigation. Despite considerable extension efforts over successive decades, current evidence indicates that failure to provide the new-born calf with sufficient high-quality colostrum is common. To understand the reasons for suboptimal colostrum feeding requires social research, with appropriate extension strategies developed to elicit practice change. Although there can be little doubt regarding the importance of heifer rearing to the profitability and sustainability of the farming business, the collective literature points to a failure of retrospective analyses in determining the cause of poor heifer performance. In reality, it is likely to be a combination of factors. The objective of this review is to investigate the effect of liveweight gain at various stages of the growth cycle of the heifer on the milk-production capacity of the lactating animal.
... With regards the effect of Lwt at first breeding on reproduction and animal longevity, both (Archbold et al. 2012) and McNaughton and Lopdell (2013) reported an effect of heifer Lwt at 15 months on time to pregnancy; however, at least in the case of (Archbold et al. 2012), this effect reflected the number of heifers that had not attained puberty at the onset of the seasonal breeding season and was not an effect of heifer Lwt, per se. Of course, as puberty is influenced by Lwt (Foldager et al. 1988, Peri et al. 1993, Niezen et al. 1996, it must be acknowledged that too low a Lwt gain pre-puberty, which results in heifers not having reached puberty by planned start of breeding, will delay breeding, delay first calving, and reduce the likelihood of pregnancy during the first lactation; this was reflected in a lower longevity in first and second lactation in the lowest heifer Lwt quartile (Archbold et al. 2012). Nonetheless, in their dataset, as long as the heifers were at a sufficient Lwt to attain puberty before breeding, time to a successful pregnancy and longevity of the animal did not vary. ...
... In general, the regime resulted in greater feed conversion efficiency, greater mammary secretory development, and generally resulted in greater milk production (~10%). Others have confirmed the presence of compensatory growth in stature in dairy heifers, when two months of ad libitum feeding followed four months of a restricted allowance (Peri et al. 1993, Barash et al. 1994. However, the effect on milk production was not consistent; (Barash et al. 1994) reported no effect of rearing method on milk production, while (Peri et al. 1993) identified a 16% increase in milk yield and a 9% and 2% increase in milk fat and protein yields, respectively. ...
... Others have confirmed the presence of compensatory growth in stature in dairy heifers, when two months of ad libitum feeding followed four months of a restricted allowance (Peri et al. 1993, Barash et al. 1994. However, the effect on milk production was not consistent; (Barash et al. 1994) reported no effect of rearing method on milk production, while (Peri et al. 1993) identified a 16% increase in milk yield and a 9% and 2% increase in milk fat and protein yields, respectively. Similarly, Ford and Park (2001) reported 1.5 fold increase in growth efficiency (Lwt gain/DM intake) and a 21% and 15% increase in first and second lactation yield, respectively, in animals subjected to repeating periods of restriction and realimentation. ...
Dairy heifer growth and live weight at first calving are regarded as important management variables affecting profitability and animal welfare. However, the appropriateness of heifer growth rate targets for different farming systems is not clear. Retrospective assessments of the association between heifer live weight and subsequent productivity indicate significant benefits in milk production and, even, reproduction from increasing live weight at breeding and first calving. Prospective interventionist experiments do not concur, however, with very variable effects of live weight at breeding on milk production and only limited evidence of a positive effect of first calving live weight on first lactation milk yield. In addition, any benefit in the first lactation is not evident in subsequent lactations in the limited number of long-term studies reported. Pre-weaning nutrition and average daily weight gain are areas of increasing interest, with lifelong increases in milk production resulting from accelerated growth rates during the first eight weeks of life indicating possible significant return from a short-term investment. This could be one reason for the inconsistent effects of heifer live weight at breeding and first lactation on milk production. Although the effect of pre-weaning average daily gain on heifer live weight is short-lived, a recent meta-analysis indicates that pre-weaning average daily gain explains 22% of the variation in first lactation milk production. The validity of these results in grazing systems requires investigation. Despite considerable extension efforts over successive decades, current evidence indicates that failure to provide the new-born calf with sufficient high quality colostrum is common. To understand the reasons for suboptimal colostrum feeding requires social research, with appropriate extension strategies developed to elicit practice change. Although there can be little doubt regarding the importance of heifer rearing to the profitability and sustainability of the farming business, the collective literature points to a failure of retrospective analyses in determining the cause of poor heifer performance. In reality, it is likely to be a combination of factors. The most likely nutritional factors are discussed in this review. BACKGROUND Dairy heifer growth rate and live weight (Lwt) at first calving are regarded as important benchmarks in farm management (Sejrsen and Purup, 1997) because lower Lwt heifers are at a greater risk of dystocia at first calving (Mee et al. 2008), produce less milk, and have a shorter lifespan in the herd (Archbold et al. 2012, McNaughton and Lopdell 2013). Also, greater heifer growth rates can theoretically lead to an earlier breeding event and reduce the time that the heifer spends in a non-productive state (Capuco et al. 1995, Sejrsen and Purup 1997). However, there is evidence that excessive growth rates at key periods of development are associated with impaired mammary development and reduced milk production (Harrison et al. 1983, Sejrsen et al. 1983, Sejrsen and Purup 1997). Therefore, the rate of growth must be planned to ensure that heifers become productive early, without undermining lifetime productivity. To complicate matters, recommendations on optimum first-calving Lwt vary widely. In high concentrate intensive feeding systems, Holstein-Friesian cows achieve 550 to 650 kg of Lwt before first calving (Keown and Everett, 1986; Heinrichs, 1993; Hoffman, 1997), while a more modest first-calving Lwt is accepted in pasture-based systems for the same breed (450 to 550 kg; McLean and Freeman 1996, Holmes et al. 2002). Troccon (1993) recommended that a heifer's Lwt at first calving should be 90% of her mature Lwt. However, how should mature Lwt be determined? The average of the herd does not account for the heifer's individual genetics and is heavily influenced by the environment in which the herd is managed. In addition, (Archbold et al. 2012) reported that low Lwt heifers at 15 months remained low Lwt heifers at first calving and as cows up to at least their third lactation. In fact, in their dataset, all heifers were 85% of their five year old Lwt at first calving, irrespective of the quartile of 15 month Lwt they belonged to; herd mature Lwt could, therefore, be a function of historical heifer growth trajectory and projecting heifer growth on data from cows that were poorly grown as heifers
... There is no doubt that nutrition is a major factor for the variation in age at onset of puberty (for reviews, see Moran et al. 1989;Robinson, 1990;Schillo et al. 1992). The impact of nutrition is illustrated by the results of one of our experiments, in which wide variation in daily growth rate was achieved by varying the feeding level (Foldager et al. 1988). ...
... In contrast, average live weight at first oestrus was unaffected by feeding level. These results clearly confirm that reproductive development in cattle, as in humans (Frisch, 1984), is more closely related to body development than to chronological age (see Moran et al. 1989 andSchillo et al. 1992). Consequently, it is very important to consider this relationship when interpreting data concerning the influence of nutrition on mammary growth. ...
... E. Mantysaari, V. Toivonen, K. L. Ingvartsen & K. Sejrsen, unpublished results). The same conclusion is evident in experiments investigating the effect of feeding level during rearing on subsequent milk potential of heifers (Foldager & Sejrsen, 1991;Peri et al. 1993). ...
The available studies concerning the relationships between nutrition, puberty and mammary development demonstrate the importance of pubertal mammary growth for the future development and ultimate milk-producing capacity of the mammary gland. A relationship between reproductive development and mammary development is also evident and mammary development at puberty is clearly influenced by the feeding level at that time. The role of specific nutrients has not been thoroughly investigated, but results suggest that specific fatty acids may be involved in the regulation of mammary growth. Mammary growth during puberty is affected by oestrogen and GH, but their respective roles and mechanisms of action have not yet been clarified.
... In dairy cattle, the effect of alternating periods of nutrient restriction during the post-weaning stage, followed by a re-feeding stage, is still unclear. In some cases, heifers that were initially restricted in their nutrient intake but were later subjected to compensatory growth reached puberty at a similar age as heifers that were always provided with 100% of their requirements (56)(70) , but in other cases they were delayed by a few months (32)(71) . Of note, in all studies the BW at which heifers reached puberty did not differ between feeding strategies. ...
... P < 0.01; Figure 2a), while the correlation between ADG and BW at puberty was lower and positive (r = 0.33, P < 0.01; Figure 2b). In this sense, as previously reported in dairy cattle (56) (57) (58) , as heifers gained more BW, the age at puberty decreased, which implies a relevant effect of nutritional level and/or factors that determined changes on feeding intake (e.g. social environment) during females rearing on the onset of cyclic activity. ...
Management practices during the rearing of dairy heifers should allow an adequate body growth and reproductive development to attain puberty several months before the first conception. Proposed target age and body weight (BW) at first calving for Holstein heifers are between 22-24 months and 82% of mature BW, respectively, for which heifers must conceive at around 15 months of age with 60% of their mature BW. Pre- and postweaning feeding level has effects on feed efficiency, behavior, energy metabolism and body and reproductive development, while social environment during rearing, specifically the social dominance and social regroupings, is known to affect energy metabolism, feeding behavior and body and reproductive development of the heifer. In Uruguay, the information published regarding the management of the dairy heifer is scarce. The aim of this review is to briefly assess the main factors affecting the onset of puberty, and to present an integrative approach of the information generated in Uruguay regarding the effects of modifying the feeding level and social environment during the rearing period on body development, metabolism, and onset of puberty in dairy heifers. In addition, we make a proposal of knowledge gaps that should be addressed in future studies.
... n. Gaynor et al., 1995, Gardner et al. (1988), Head et al. (1991), Peri et al. (1993), Troccon (1993), Gaynor et al. (1995) sowie Müller u. a. (2007). Die Gründe in den z.T. widersprüchlichen Untersuchungsergebnissen bezüglich der Wirkungen unterschiedlicher Fütterungsintensität der Kälber und Jungrinder vor der Pubertät auf die spätere Milchleistung sehen Sejrsen und Purup (1997) ...
... Trotz der Zunahmen im ersten Jahr von nahezu 900 g/d ist ein ungünstiger Einfluss aufgrund der zu unterstellenden erhöhten Fetteinlagerung im Eutergewebe nicht feststellbar. Auch bei Waldo et al. (1986); Park et al. (1987); Gardner et al. (1988), Head et al. (1991); Peri et al. (1993); Troccon (1993); Gaynor et al. (1995); Steinhöfel und Steinhöfel (2006) sowie Müller u. a. (2007) ließ sich ein solches Leistungsverhalten nicht feststellen. Die Ursachen für die widersprüchlichen Untersuchungsergebnisse können dabei durchaus unterschiedlicher Natur sein. ...
... Many of these studies are outdated or utilized different breeds of dairy cattle, making inferences to the modern Holstein genotype difficult. Figure 1 represents five recent studies (9,13,14,15,16) These data (9,13,14,15,16) suggest the effects of early calving on first lactation milk yield are predictable, but causative mechanisms are not predictable. It is, however, important to remember that all of these studies demonstrate that there is little or no benefit to first lactation milk yield by delaying calving beyond 24 months. ...
... Many of these studies are outdated or utilized different breeds of dairy cattle, making inferences to the modern Holstein genotype difficult. Figure 1 represents five recent studies (9,13,14,15,16) These data (9,13,14,15,16) suggest the effects of early calving on first lactation milk yield are predictable, but causative mechanisms are not predictable. It is, however, important to remember that all of these studies demonstrate that there is little or no benefit to first lactation milk yield by delaying calving beyond 24 months. ...
... Heifers in the GF+1% CR treatment showed a higher DWG compared to the other treatments. The improved growth rate in heifers supplemented with concentrate is consistent with findings from previous studies by Choi et al. (1997), Jin et al. (2004), Yambayamba and Price (1997), Peri et al. (1993), Park et al. (1998), Ford andPark (2001), and others. These studies also reported that dietary treatments have an impact on growth and the onset of puberty. ...
This study aimed to investigate the effects of varying levels of concentrate ration on the performance of Sahiwal heifers during the pre-pubertal period. The study examined several key parameters, including dry matter intake (DMI), daily weight gain (DWG), feed efficiency (FE), onset of puberty, body measurements (BM), and nutrient digestibility. The findings demonstrated significant differences among the different treatments and provided valuable insights into the impact of concentrate supplementation. Regarding DMI, the results indicated a variation ranging from 3.66±0.08 to 5.59±0.03 kg/heifer, which could be attributed to factors such as age, size, and weight of the heifers. In terms of DWG, heifers fed on a diet consisting of green fodder and 1% concentrate exhibited a higher average daily weight gain of 0.49±0.01 kg/calf compared to other treatments. FE was also influenced by the level of concentrate supplementation, with higher concentrations leading to improved efficiency. The provision of additional dietary protein was found to enhance feed efficiency by converting feed into available protein. The onset of puberty was significantly affected by the supplementation of green fodder with varying levels of concentrate. Delayed puberty was observed in Sahiwal heifers fed solely on ad-libitum fodder, indicating the importance of sufficient nutrient intake to meet the heifers' nutritional requirements. Body measurements (BM), including body length (BL), wither height (WL), and heart girth (HG), showed improvement in heifers fed on varying levels of concentrate. The digestibility of nutrients, including dry matter (DM), crude protein (CP), ether extract (EE), and ash, varied significantly among the different treatments. Overall, this study provides important insights into the effects of concentrate ration levels on the performance of Sahiwal heifers during the pre-pubertal period. These findings contribute to existing knowledge and can serve as a valuable resource for researchers, farmers, and stakeholders interested in optimizing the growth and development of Sahiwal heifers.
... Swanson (1960) using Jerseys, andLittle andKay (1979) using British Friesians, demonstrated a 15 to 48% decrease in 1 st -lactation milk yield by heifers fed high energy diets for higher rates of an average daily gain (ADG). Heifers fed for an ADG in excess of 700 g/day during the prepubertal period had reduced milk yield during first lactation (Gardner et al., 1977;Bettenay, 1985;Peri et al., 1993). The accelerated pre-pubertal growth from 700 to 1000 g/day in Holstein heifers decreased subsequent 1 st -lactation fat-corrected milk yield 7.1% (Lammers et al., 1999). ...
The main goal of this study was to determine the effects of body weight traits during the rearing period on subsequent milk production of primiparous dairy cows using Principal Component Analysis. Data on lactation performance records of 109 Red Steppe dairy cow progeny of six bulls maintained at the State Enterprise “Pedigree Reproducers” Stepove”” (Mykolayiv region, Ukraine), during 2001–2014, were utilised for the present study. Heifer body weight at birth, 3, 6, 9, 12, 15, and 18 months of age was measured. Records of 305-day milk yield (kg), milk fat percentage (%), milk fat yield (kg), monthly milk yield (kg) and milk fat percentage (%) in the 1st-lactation dairy cows were also available. Principal Components Analysis (PCA) was conducted on the live weights for each heifer between birth and 18 months of age. The first three principal components (PC1-PC3) explained 79.7% of the total variance. Principal component 1 (PC1) showed significant relationship to body weight of heifers at 9, 12, and 15 months of age (post-pubertal period).
Body weight at 3 and 6 months of age (pre-pubertal period) had higher scores on the second principal component (PC2). Principal component 3 (PC3) showed significant relationship to body weight of calves at birth. Only groups of heifers with high scores on PC1 and PC2 had significant effect on subsequent milk performance (with the exception of milk fat percentage). Thus, the use of a multivariate technique (Principal Component Analysis) allowed to determine two age intervals of heifers during the rearing period (pre- and postpubertal periods), which were significantly related to subsequent milk production.
... Swanson (1960) using Jerseys, andLittle andKay (1979) using British Friesians, demonstrated a 15 to 48% decrease in 1 st -lactation milk yield by heifers fed high energy diets for higher rates of an average daily gain (ADG). Heifers fed for an ADG in excess of 700 g/day during the prepubertal period had reduced milk yield during first lactation (Gardner et al., 1977;Bettenay, 1985;Peri et al., 1993). The accelerated pre-pubertal growth from 700 to 1000 g/day in Holstein heifers decreased subsequent 1 st -lactation fat-corrected milk yield 7.1% (Lammers et al., 1999). ...
The main goal of this study was to determine the effects of body weight traits during the rearing period on subsequent milk production of primiparous dairy cows using Principal Component Analysis. Data on lactation performance records of 109 Red Steppe dairy cow progeny of six bulls maintained at the State Enterprise “Pedigree Reproducers” Stepove”” (Mykolayiv region, Ukraine), during 2001–2014, were utilised for the present study. Heifer body weight at birth, 3, 6, 9, 12, 15, and 18 months of age was measured. Records of 305-day milk yield (kg), milk fat percentage (%), milk fat yield (kg), monthly milk yield (kg) and milk fat percentage (%) in the 1 st -lactation dairy cows were also available. Principal Components Analysis (PCA) was conducted on the live weights for each heifer between birth and 18 months of age. The first three principal components (PC1-PC3) explained 79.7% of the total variance. Principal component 1 (PC1) showed significant relationship to body weight of heifers at 9, 12, and 15 months of age (post-pubertal period). Body weight at 3 and 6 months of age (pre-pubertal period) had higher scores on the second principal component (PC2). Principal component 3 (PC3) showed significant relationship to body weight of calves at birth. Only groups of heifers with high scores on PC1 and PC2 had significant effect on subsequent milk performance (with the exception of milk fat percentage). Thus, the use of a multivariate technique (Principal Component Analysis) allowed to determine two age intervals of heifers during the rearing period (pre- and postpubertal periods), which were significantly related to subsequent milk production.
... The main source of within-breed variation in age at onset of puberty is level of feeding (see reviews by Moran et al., 1989;Robinson, 1990;Schillo et al., 1992). In supporting to these findings, Mantysaari et al., 1995 andSejrsen et al., 1998 shown that an excessive feeding before puberty can impair mammary development and decease subsequent milk yield as reported by (Peri et al., 1993 andRadcliff et al., 2000). On applied experiment, Borghese et al., (1997) found that buffalo heifers reared on pasture system (unexcessive feeding) promoted the best performance in heifers, because of the economy of feeding with favorable daily gain and early age at puberty and at conceiving. ...
... However, when this was done immediately after weaning, mammary parenchymal (PAR) tissue mass and DNA content in Holstein calves decreased by 23 and 32%, respectively [6]. The detrimental effects of increased pre-pubertal nutrient intake (starting post-weaning) on mammary development have long been recognized [7][8][9][10], and recently [6] confirmed in various studies [11][12][13][14][15][16]. Furthermore, the negative effect on mammary development may translate into poorer first lactation performance, as a recent study confirmed that heifers fed at a greater rate produced 14% less milk compared with controls [17]. ...
Background: To reduce costs of rearing replacement heifers, researchers have focused on decreasing age at breeding and first calving. To increase returns upon initiation of lactation the focus has been on increasing mammary development prior to onset of first lactation. Enhanced plane of nutrition pre-weaning may benefit the entire replacement heifer operation by promoting mammary gland development and greater future production.
Methods: Twelve Holstein heifer calves (< 1 week old) were reared on 1 of 2 dietary treatments (n = 6/group) for 8 weeks: a control group fed a restricted milk replacer at 0.45 kg/d (R, 20% crude protein, 20% fat), or an accelerated group fed an enhanced milk replacer at 1.13 kg/d (EH, 28% crude protein, 25% fat). At weaning (8 weeks), calves
were euthanized and sub-samples of mammary parenchyma (PAR) and mammary fat pad (MFP) were harvested upon removal from the body. Total RNA from both tissues was extracted and sequenced using the Illumina HiSeq2500 platform. The Dynamic Impact Approach (DIA) and Ingenuity Pathway Analysis (IPA) were used for pathway analysis and functions, gene networks, and cross-talk analyses of the two tissues.
Results: When comparing EH vs R 1561 genes (895 upregulated, 666 downregulated) and 970 genes (506 upregulated, 464 downregulated) were differentially expressed in PAR and MFP, respectively. DIA and IPA results highlight a greater proliferation and differentiation activity in both PAR and MFP, supported by an increased metabolic activity. When calves were fed EH, the PAR displayed transcriptional signs of greater overall organ development, with higher ductal growth and branching, together with a supportive blood vessel and nerve network. These activities were mediated by intracellular cascades, such as AKT, SHH, MAPK, and Wnt, probably activated by hormones, growth factors, and endogenous molecules. The analysis also revealed strong communication between MFP and PAR.
... Consequently, various reports have shown that rapid rearing by feeding high-concentrate diets not only reduces the age of sexual maturity but also decreases the time period it takes to reach the age of first calving (Gardner et al., 1977;Hoffman et al., 1996Hoffman et al., , 2007. However, high energy diets may cause undesirable fat deposition, thereby affecting mammary development and future milk yield potential (Sejrsen et al., 1982;Peri et al., 1993;Brown et al., 2005). Therefore, limit feeding has drawn attention in recent years because it offers great potential to reduce the costs associated with raising replacement dairy heifers. ...
The objective of this study was to evaluate the effects of dietary physically effective neutral detergent fiber (peNDF) content on the feeding behavior, digestion, ruminal fermentation parameters, and growth of 8- to 10-mo-old dairy heifers and to predict the adequacy of dietary fiber in growing dairy heifers. Twenty-four Holstein dairy heifers (245 ± 10.8 d of age, 305.6 ± 8.5 kg initial live weight) were randomly divided into 4 treatments with 6 replicates as a completely randomized design. During the 60-d period with a 10-d adaptation, heifers were offered 1 of 4 diets, which were chemically identical but included different peNDF8.0 (particle size is >8 mm and <19 mm) content (% DM): 10.8, 13.5, 18.0, or 19.8%, which was achieved by chopping forage into different lengths (fine = 1 cm, short = 3 cm, medium = 5 cm, and long = 7 cm). The concentrate and silage were mixed and fed restrictedly and exclusive of forage (Chinese ryegrass hay) were offered ad libitum. The body weight and frame size of the heifers were measured every 15 d during the experimental period. Samples of the rumen content (2 h after the morning feeding) were taken for pH, ammonia, and volatile fatty acid determination. The dry matter intake and average daily gain of the heifers were not significantly affected by peNDF8.0 content. The body frame size (including withers height, body length, and heart girth) of the heifers was not increased significantly by enhanced peNDF8.0 content. Ruminal pH and ammonia concentration were both increased with increasing dietary peNDF8.0 content. The ruminal total volatile fatty acid concentration and percentage of acetate and butyrate profiles were not significantly affected by dietary peNDF8.0 content. However, the enhanced peNDF8.0 content led to a decrease in the propionate percentage. The ratio of acetate to propionate in the 13.5% treatment was highest among the treatments. Increasing the particle size and dietary peNDF8.0 content resulted in increased eating and chewing time but had no effect on rumination time. Heifer total eating and chewing time and eating and chewing time per kilogram of dry matter intake were increased with increasing dietary peNDF8.0 content. The apparent digestibility of acid detergent fiber and crude protein was improved with an increasing content of dietary peNDF8.0. The results suggest that an optimal or advisable dietary particle size and peNDF8.0 content improves chewing activity, rumen fluid pH, and ruminal fermentation. The data based on feeding behavioral and growth responses of heifers as well as rumen fermentation and digestion by improving total eating and chewing time indicate that 18.0% dietary peNDF8.0 content is the most suitable for 8- to 10-mo-old Holstein heifers.
... Zwischen ASAT und Milchleistung waren Der Einfluss der Ernährungsintensität während der Aufzucht auf die nachfolgende Milchleistung wurde bereits in früheren Arbeiten untersucht. In einigen Untersuchungen zeigte sich, dass eine hohe Ernährungsintensität, die sich in entsprechend hohen täglichen Zunahmen widerspiegelt, die Milchleistung nachteilig beeinflussen kann (Hansson et al., 1953;Foldager und Sejrsen, 1983;Peri et al., 1993;Andreae und Müller, 1997;Van Amburgh et al., 1998;Macdonald et al., 2005). Diese nachteiligen Effekte waren aber nicht gleichmäßig über die gesamte Aufzuchtperiode verteilt, sondern konzentrierten sich auf einen Abschnitt, in welchem die Tiere zwischen 150 bis 300 kg wogen. ...
Using 15 pairs of female monozygotic Holstein Friesian twins that received diets containing different energy contents we repeatedly detected blood biomarkers (insulin, glutamate dehydrogenase, aspartate aminotransferase) and body traits (back fat thickness, daily weight gain). The study reached until the age of 660 days. No effect of a different feeding on milk yield was found. However, the different diet caused effects on daily weight gains, back fat thickness and insulin levels (p<0, 0001). Insulin reached much sooner higher concentrations in the group with intensive feeding than in the group with moderate feeding. Comparing pairs of twins with high (10323kg) and low (7857kg) milk yield during the rearing period we found to 37% higher insulin and to 27% lower aspartate aminotransferase levels in the high performance group than in the group with low milk yield. Probably these effects are genetically determined.
... Lorsque la ration est enrichie ou appauvrie en énergie au-delà de 196 jours, aucune différence n'est observée entre traitements. Par ailleurs, des génisses rationnées, puis nourries à volonté peu de temps avant la puberté attendue, présentent leurs premières chaleurs 22 jours avant les génisses témoins (Peri et al 1993). Une des hypothèses avancées est que pendant leur courte période de compensation, et en raison à la fois d'un métabolisme basal réduit et donc d'un surplus d'énergie et de protéines lors de la réalimentation (Hornick et al 2000), elles pourraient déposer davantage de lipides, favorable au déclenchement de la puberté, comme cela a été rapporté dans d'autres espèces (Frisch 1984). ...
On dairy farms, rearing heifers is aimed at having efficient milking cows, from reproductive, productive and longevity points of views. The animals also need to be adapted to their living environment and to be reared at the lowest cost possible. Practical solutions exist and the present paper is an update of rearing dairy heifer procedures, from birth to first calving, and their subsequent performances. Age at first calving (24, 30 or 36 months of age in seasonal calving systems for example) is of importance when considering the dairy system. With first calving at 24 months of age, puberty should arise early and body development and reserve should be adequate. However, a too high growth rate should be avoided because of possible excessive fatness that could have a deleterious effect on long-term performances. With calving at 30 or 36 months of age, growth intensity could be reduced, particularly when animals are housed during the winter. But insufficient growth performances (400 g/d or less) could be deleterious for reproduction and longevity. The grazing system, optimising compensatory growth capacity of heifers, can reduce rearing costs significantly. When seasonal calving procedures are used in the herd, hormonal treatment could be useful. Reducing even more the age at first calving (20 months or less), resulting in low rearing and labour costs... is probably of interest but has to be studied in detail.
... Lorsque la ration est enrichie ou appauvrie en énergie au-delà de 196 jours, aucune différence n'est observée entre traitements. Par ailleurs, des génisses rationnées, puis nourries à volonté peu de temps avant la puberté attendue, présentent leurs premières chaleurs 22 jours avant les génisses témoins (Peri et al 1993). Une des hypothèses avancées est que pendant leur courte période de compensation, et en raison à la fois d'un métabolisme basal réduit et donc d'un surplus d'énergie et de protéines lors de la réalimentation (Hornick et al 2000), elles pourraient déposer davantage de lipides, favorable au déclenchement de la puberté, comme cela a été rapporté dans d'autres espèces (Frisch 1984). ...
En élevage laitier, l'éleveur doit réussir à amener ses génisses de renouvellement à être de bonnes femelles laitières (notamment des points de vue de la production, de la reproduction et de la longévité), adaptées aux conditions d'élevage et au système de production, et ce, au moindre coût de production. Ceci reste une gageure, mais des solutions existent. Le présent article se propose de faire le point sur celles-ci, en s'intéressant particulièrement aux conditions d'élevage et aux différentes étapes clés de l'élevage de la génisse laitière, de sa naissance jusqu'au premier vêlage. Certaines informations allant au-delà (réforme par exemple) complètent cette approche. L'article reprend et réactualise les données existantes depuis plusieurs décennies, notamment en ce qui concerne l'alimentation de la future vache laitière. La maîtrise de l'âge au 1er vêlage (24, 30 ou 36 mois dans le cas des vêlages groupés), selon le système de fourrage considéré ou en place dans les élevages, s'avère cruciale. Dans le cas d'un vêlage à 24 mois d'âge, une puberté acquise précocement, une cyclicité maintenue, un bon état d'engraissement et un bon développement aux différents stades sont des objectifs à atteindre dans les meilleures conditions possibles pour le succès de cette pratique. Ceux-ci dépendent grandement des programmes alimentaires et des races, mais il est important d'éviter un engraissement excessif qui pourrait être pénalisant pour la suite de la carrière. Dans le cas d'un vêlage à 30 ou 36 mois des rythmes de croissance plus modérés, notamment en période de stabulation, sont possibles, à condition de ne pas descendre trop bas en terme de croissance journalière (400 g/j ou moins), pour ne pas affecter la reproduction et la carrière des vaches. Les régimes alimentaires à base d'herbe et exploitant les capacités de croissance compensatrice des animaux permettent de réduire significativement et efficacement les coûts d'élevage. Dans le cas de vêlages groupés ou lors de la conduite en lots, la pratique alimentaire peut être accompagnée de traitements hormonaux (PGF2a ou analogues, progestagènes). Réduire encore plus l'âge au vêlage vers 20 mois d'âge, avec une réduction des coûts, des rejets, du travail... est sans doute possible et cette possibilité nécessitera d'être testée dans les années à venir.
... One of the keys when feeding growing ruminants is to ensure the development of adequate frame size and muscle structure prior to puberty without becoming too fat. There are various strategies in use to accomplish this (15,17,24). The 1989 Dairy National Research Council (14) report includes requirements for ruminally degradable intake protein (DIP) and ruminally undegradable intake protein (UIP) for growing animals as well as lactating cows. ...
... Their second restriction occurred during gestation and was followed by a period of compensatory gain in late gestation. Peri et al. (1993) observed an increased milk production in calves developed on a single-phase stair-step program; however, the restriction occurred at a younger age (6 to 10 mo) than our heifers. Piantoni et al. (2012) demonstrated that plane of nutrition in the preweaned dairy heifer (approximately 65 d of age) resulted in differential gene expression in both parenchymal tissue (n = 1,641) and mammary fat pad (n = 1,541). ...
Replacing cows in the herd is second only to nutrition as the single greatest input cost in cow/calf beef production. The increased availability of cereal grains for feeding livestock has allowed replacement heifers to enter the production system at younger ages. Many heifer development programs feed to ensure heifers reach puberty before the time that they are mated to calve at 2 yr of age. Nutrition level during development has been associated with altered milk production and stayability. We hypothesized that heifers exposed to a lower nutrition level during the peripubertal period would have less methylation of the DNA in the mammary gland and ovarian cortex. We also hypothesized that the ovarian reserve would decrease in heifers fed for rapid growth compared to heifers fed for slow growth during puberty. At 257 ± 1 d of age, heifers in the Stair-Step treatment (n = 6) received 157 kcal ME/BW kg(0.75) for 84 d and heifers in the Conventional treatment (n = 6) were offered 228 kcal ME/BW kg(0.75). At d 84, heifers were fed for an additional 83 d. Stair-Step heifers were offered 277 kcal ME/BW kg(0.75), and heifers on the Conventional treatment received 228 kcal ME/BW kg(0.75). Mammary weights (P = 0.43), capillary area density (P = 0.74), and capillary surface density (P = 0.18) did not differ between treatments and neither did alveolar number (P = 0.55) and alveolar density (P = 0.49). Reproductive tract weights (P = 0.69) and ovarian weight (P = 0.68) and ovarian size (P > 0.75) did not differ between treatments. In histological sections, Stair-Step heifers had more primordial follicles than Conventional heifers (P = 0.02), but primary (P = 0.59) and secondary (P = 0.15) follicles did not differ. Global methylation of parenchymal tissue (P = 0.82), mammary fat pad (P = 0.45), and ovarian cortex (P = 0.14) did not differ between treatments. Anterior pituitary weight did not differ between treatments (P = 0.16). Our hypothesis that modifying peripubertal nutrition modifies global methylation of the mammary and ovary is not supported; however, our hypothesis that it modifies the ovarian reserve is supported.
... This concern comes primarily from one study (Sejrsen et al., 1982), involving 10 heifers and two levels of nutrition during the prepubertal period, in which heifers that grew at a rate of 2.86 lb/day had lower secretory cells than those that grew at a rate of 1.43 lb/day. There are also some other studies that have reported decreases in milk yield when applying rapid ADG to heifers (Swanson, 1960;Gardner et al., 1977;Little and Kay, 1979;Van Amburgh et al., 1998;Radcliff et al., 2000), but there are also several studies that reported no change in milk yield (Lacasse et al., 1993;Hoffman et al., 1996;Radcliff et al., 1997;Waldo et al., 1998) and others that reported an increase in milk yield (Peri et al., 1993;Stelwagen and Grieve, 1992). Recently, Daniels et al. (2009) evaluated the effect of ADG (ranging from 1.43 to 2.09 lb/ day) on mammary development and concluded that BW and age are the most important factors affecting mammary development, with rate of growth having a minimal impact. ...
Dairy replacement heifers not only define the long-term future of the dairy enterprise, but they also represent close to 10% of the costs associated with milk production. Optimizing heifer growth has an impact on herd profitability through cost rationalization and improved performance of the future herd. Potential areas for improvement appear early in life with the provision of adequate amounts of good-quality colostrum. In addition, there is evidence that growth rate during the first 2 mo of life is positively correlated with future milk production. Growth rate early in life can be accomplished by improving nutrient supply from milk or milk replacer and concomitantly fostering intake of solid feed through palatable starters, appropriate feeding devices, and social facilitation. At later stages of growth, regrouping slow-growing heifers by maintaining them in the same pen and introducing a relatively large number of unacquainted, younger, and lighter-weight animals results in improved average daily gain of the old slow-growing heifers. Because age at first calving (between 22 and 28 mo) has no relationship with future milk yield and incidence of calving problems, a logical target would be reaching first calving at 22 mo. However, since body weight (BW) at calving does have an impact on future milk yield, it is important that a minimum BW of 1550 lb is attained at calving (22 mo). This target implies gains around 1.87 lb/day. For some years, there has been some concern about fast average daily gain (ADG) and potential detrimental effects on udder development and future milk yield. However, recent evidence indicates that gains as high as 2.64 lb/day not accompanied by fattening, have no negative effect on future milk yield provided adequate protein to energy ratios are fed. Last, it has been commonly recommended that heifers are bred with BW equivalent to 55% of their mature BW. However, there have been no attempts to forecast the mature BW of a given animal at breeding time. A recent study indicates that mature BW can be forecast using growth data from an individual animal using a Gompertz non-linear model. Preliminary data suggest that small-frame heifers might produce more milk if bred at 55% of their predicted mature BW, whereas large-frame heifers would produce more milk if bred around 60% of their predicted mature body weight (MBW). This article covers some of the above-mentioned aspects and other management and feeding strategies that can be implemented in heifer rearing to improve future milk yield and overall profitability of the dairy enterprise.
... In order to achieve this, high energy, high protein, and thus, high concentrate diets are being fed to accelerate growth rates of calves and heifers. Various reports have shown that when accelerated diets are fed before puberty then breeding age and AFC but also firstlactation milk yield (MY) decrease (Gardner et al., 1977;Peri et al., 1993;Hoffman et al., 1996;Sejrsen and Purup, 1997;Radcliff et al., 2000). ...
This review focuses on the nutritional effects from birth until age at first calving on growth, mammary developmental changes, and first-lactation milk yield in heifer calves. The advancement in the genetic potential and the nutritional requirements of the animals has hastened the growth rate. Genetic selection for high milk yield has suggested higher growth capacity and hence increasing nutritional inputs are required. Rapid rearing by feeding high energy or high concentrate diets not only reduces the age of sexual maturity but also lowers the time period of attaining the age of first calving. However, high energy diets may cause undesirable fat deposition thereby affecting future milk yield potential. Discrepancies exist whether overfed or overweight heifers at puberty can influence the mammary development and future milk yield potential and performance. The data on post-pubertal nutritional management suggested that body weight at calving and post-pubertal growth rate is important in first lactation milk yield. There is a continuous research need for strategic feeding that accelerates growth of dairy heifers without reduction in subsequent production. Nutritional management from birth, across puberty and during pregnancy is critical for mammary growth and for producing a successful cow. This review will mostly highlight studies carried out on dairy breeds and possible available opportunities to manipulate nutritional status from birth until age at first calving.
... In the present trial heifers weighed between 128 and 157 kg at the same age, indicating that they are also under weight in terms of American growth standards. Israeli heifers (Peri et al., 1993) weighed 244, 275 and 304 kg at approximately 10 months of age after receiving diets described as restricted (85% of NRC, 1989 recommendations), control and ad libitum intakes. Live weights of these heifers were similar to those obtained at 12 months in the present study, probably indicating that South African bred Holsteins are smaller than Israeli Holsteins. ...
At two months of age, 48 Holstein-Friesland heifers were randomly allocated to four treatments comprising untreated wheat straw (WS), oven-ammoniated wheat straw (AWS), lucerne hay (LH) or oat hay (OH). Least cost nutrient balanced complete diets were formulated for heifers of different age groups, i.e. 2–6, 6–10, 10–13, 13–18 months and 18 months to first calving. Dry matter (DM) intakes of individual heifers were determined twice weekly. Animals were weighed once weekly, and girth circumference and wither height were measured monthly. From 13 months of age, heifers were observed daily for oestrus and inseminated provided that a minimum live weight of 290 kg had been attained. At two months of age, heifers weighed (mean ± s.e.) 69 ±1.1 kg and wither height and girth circumference measured 84.6 ± 0.4 and 94.1 ± 0.6 cm respectively. The average daily gain of heifers receiving diets containing LH was higher (P < 0.001) from two months of age to calving than that of heifers receiving diets containing WS, AWS or OH (0.76 vs. 0.68, 0.64 and 0.68 kg/day respectively). Heifers receiving LH diets were heavier (P < 0.001) at first calving than heifers fed diets containing other roughages. Wither height at 22 months of age did not differ (P > 0.05) between treatments, the overall mean being 129.3 ± 0.5 cm. Girth circumference of heifers fed diets containing WS, AWS and OH was smaller (P < 0.001) than that of heifers fed LH (179.2, 177.3 and 176.7 cm vs. 188.3 cm respectively). Heifers fed diets containing LH also had higher (P < 0.01) condition scores than heifers fed diets containing other roughages. The lower feeding cost of AWS diets in comparison to other diets should be utilized fully in the rearing of replacement heifers.
... Zwischen ASAT und Milchleistung waren Der Einfluss der Ernährungsintensität während der Aufzucht auf die nachfolgende Milchleistung wurde bereits in früheren Arbeiten untersucht. In einigen Untersuchungen zeigte sich, dass eine hohe Ernährungsintensität, die sich in entsprechend hohen täglichen Zunahmen widerspiegelt, die Milchleistung nachteilig beeinflussen kann (Hansson et al., 1953;Foldager und Sejrsen, 1983;Peri et al., 1993;Andreae und Müller, 1997;Van Amburgh et al., 1998;Macdonald et al., 2005). Diese nachteiligen Effekte waren aber nicht gleichmäßig über die gesamte Aufzuchtperiode verteilt, sondern konzentrierten sich auf einen Abschnitt, in welchem die Tiere zwischen 150 bis 300 kg wogen. ...
... A previous report ( 1 9 ) indicated that high dietary protein may increase mammogenesis in rats. Other reports have claimed that rearing dairy heifers at accelerated rates of gain using a high protein diet had no detrimental effect on mammogenesis ( 5 ) or on subsequent lactation (20,34). Thus, results from the current experiment add support to the theory that extra dietary protein may offset the detrimental effects of high dietary energy on mammary development. ...
... Several experiments have not observed any differences in mammary development or lactation responses when ADG has been increased before puberty, in contrast to accepted theory (Peri et al., 1993;Radcliff et al., 1997;Waldo et al., 1998;Abeni et al., 2000). Recently, it has been suggested from an analysis of literature data that the discrepancy in lactation responses to ADG observed in the previously cited experiments was due to a nonlinear response profile (Zanton and Heinrichs, 2005). ...
Limit-feeding high-concentrate or high-digestibility diets for growing dairy heifers may offer an economical alterna- tive to ad libitum consumption of the high-forage, low-digestibility diets that are traditionally fed to dairy heifers. Literature pertaining to economic, physi- ological, and nutritional responses to alterations in feeding level and dietary concentrate level are reviewed. From the available research, it was found that limit-feeding higher-concentrate diets did not affect growth or first-lactation milk production compared with feeding high-forage diets when equivalent levels of gain are obtained. Dairy heifers that are limit-fed often have greater diet digestibility, lower levels of environmen- tal excretion and methane production, and greater feed efficiency. Although the digestibility was increased for heifers limit-fed high-concentrate diets, retention and excretion of N was not consistently affected. It was concluded that limit-feed- ing high-concentrate diets does not need to be excluded as a management option and may offer an opportunity for heifer growers to reduce feed costs and environ- mental output under the circumstances thus far investigated.
... Radioimmunoassays saline only (control group). Lambs were weighed at the beginning of the injection period and once a Serum concentrations of oGH (Peri et al., 1993), week thereafter until the end of the injection period. IGF-I (Breier et al., 1991) and oPL (Kann, 1971) Group feed consumption was monitored daily. ...
The somatogenic and galactopoietic effects of recombinant ovine placental lactogen (oPL) were compared with the effects of recombinant ovine growth hormone (oGH) in post-weaned growing lambs and in lactating ewes. In two experiments that each lasted 35 days, 2-month-old lambs were given daily subcutaneous injections (0.1 mg/kg live weight) of oPL or oGH, and their daily growth rates were compared with those of non-treated control lambs. Ovine GH and oPL had similar profound (P<0.01) growth-stimulating effects, enhancing lamb growth by 10 to 25%. In two other experiments, lactating ewes were injected with oGH or oPL (0.1 mg/kg live weight/day) for 14 days in mid-lactation. Treatment with oGH increased (P<0.001) daily milk production by up to 55% over control ewes. Ovine PL increased (P<0.01) milk production by up to 25%. In all experiments, treatment of lambs or lactating ewes with oGH, but not with oPL increased (P<0.05) serum insulin-like growth factor-I concentrations. It is concluded that oPL and oGH have similar somatogenic effects in lambs. Both hormones exhibited galactopoietic effects, but oGH was considerably more potent than oPL.
... Peclaris et al., 1994 Peclaris et al., , 1997 Villeneuve et al., 2010 ). Restricted feeding in the prepubertal period improves milk production in the first lactation in dairy heifers (Foldager and Sejrsen, 1991; Peri et al., 1993; Hohenboken et al., 1995; Van Amburgh et al., 1998; Lammers et al., 1999; Radcliff et al., 2000) and in dairy ewes (Zidi et al., 2005). Umberger et al. (1985) and McCann et al. (1989) observed that restricted feeding also improved the milk production of meat type breeds (Dorset and Suffolk). ...
The aim of this study was to determine the effects of restricted feeding before puberty on reproduction, lactation and offspring growth performance in replacement ewe lambs over two breeding seasons. At weaning, 41 Dorset ewe lambs were assigned to one of three diets: an ad libitum control diet with medium-quality forage (MQF; 13.3% crude protein (CP), 1.81 Mcal metabolizable energy per kg, 42.8% ADF; diet A-MQF); a restricted diet with the same forage as A but less feed concentrate (diet R-MQF); or a high-quality forage (HQF) diet (14.8% CP, 2.15 Mcal ME/kg, 34.7% ADF; diet F-HQF). The quantity of concentrate offered to the group R-MQF and F-HQF ewe lambs was adjusted to obtain 70% of the control ewe lambs' growth rate. The diets were offered for 75 days following weaning to cover the allometric phase of mammary gland development. Prepubertal restriction did not affect (P > 0.10) the gestation rate, number of lambs born or the body weight and body condition score of ewes at lambing or at the end of lactation. Ewes from groups R-MQF and F-HQF tended to produce more milk during their first lactation compared to those from group A-MQF (P = 0.07). During the second lactation, groups R-MQF and F-HQF had better standardized milk production than group A-MQF (P < 0.05), and group R-MQF produced more milk than group F-HQF (P < 0.05). Milk fat and protein content were not affected by treatments (P > 0.10) Fat and protein yield were affected by treatments only at the second lactation (P < 0.10 and P < 0.05, respectively). Lamb birth and weaning weights were not affected by prepubertal restriction of feeding in their mother (P > 0.10). However, the average daily gain of second breeding season lambs was higher for the R-MQF group than the F-HQF group (P < 0.05), and a similar trend was observed for total gain (P < 0.10). Restricted feeding before puberty does not impair future reproductive performance; however, it has a positive impact on lactation and on lambs' growth performance.
... The effect of age. First-lactation milk yield is reduced when heifers calve before two years of age (Heinrichs and Vazques-Anon, 1993;Peri et al., 1993;Ptak et al., 1993;Troccon, 1996). Milk components are also reduced when age at first calving is decreased, especially fat concentration in the milk (Pirlo et al., 1997;Abeni et al., 2000;Ettema and Santos, 2004), but protein percentage is higher (Pirlo et al., 1997). ...
Much research has been carried out and published on dairy replacement management, in order to rear heifers as efficiently as possible, from both a technical and economical point of view. In most cases, the aim is to rear the heifers at the lowest cost possible without any deleterious effects on future performances. However, the importance of dairy heifer husbandry is not sufficiently well recognized and probably mishandled by most farmers. The present review aims to give an actual overview of rearing procedures in dairy heifers and possible ways to achieve optimal goals. For many years, it has been well known that rapid rearing lowers the age of sexual maturity and consequently may be an efficient way to reduce the non-producing period prior to conception. But this may impair mammary development and consequently future milk production, at least during first lactation. In addition, a growth rate that is too low may not only be costly but also result in animals that are too fat at first calving, creating problems such as calving difficulties, dystocia, etc. Genetic considerations must also be factored, i.e. frame, size, body weight, etc. have changed during the last 20 years and there are differences between breeds. As a result, some time-honoured recommendations may not be appropriate. The present paper reviews factors and management practices that may affect rearing and subsequent performance of dairy heifers.
... Dietary restriction has a profound influence on the biology and health of animals including retardation of ageing and reduction of cancer incidence (Weindruch & Walford, 1988). While imposition of excessive dietary restriction on growing animals may inhibit normal development of the mammary gland, a well-controlled dietary energy restriction regimen positively effects mammary growth, development and subsequent lactation in rats (Park et al. 1988) and bovine species (Park et al. 1989;Peri et al. 1993;Barash et al. 1994;Choi et al. 1997). The stair-step (phased) compensatory nutrition regimen proposed and studied in our laboratory is designed so that development of mammary tissues is minimal during an energy restriction phase, while a compensatory growth phase immediately following energy restriction stimulates rapid and fuller development of the mammary gland. ...
The proper use of a time-dependent and controlled nutrition regimen during the hormone-sensitive growth phase before first parturition can significantly affect mammary growth and subsequent lactation performance. The objective of the present study was to determine if a compensatory nutrition regimen improves lactation performance by affecting proliferation and apoptosis of mammary epithelial cells. Forty female rats (7 weeks of age, average weight 148 g) were assigned to either (1) control, free access to diet or (2) stair-step compensatory nutrition regimen, an alternating 3-4-week schedule beginning with an energy-restricted diet (31.2% restriction) for 3 weeks, followed by the control diet for 4 weeks. Estimated milk yield was greater (P < 0.05) on day 15 of lactation in the compensatory nutrition group than in the control group. Mammary cell proliferation values were 1.4- and 2.7-fold greater in mammary tissue from the compensatory group during pregnant and early lactating stages respectively, compared with those from the control group. Ornithine decarboxylase (EC 4.1.17) mRNA was 24% higher (P < 0.05) in mammary tissues of rats from the compensatory nutrition group during pregnancy than in those from the control group. These results indicate that the compensatory nutrition regimen imposed during the peripubertal growth phase stimulated mammary epithelial cell proliferation and improved lactation performance.
... However, when the growth rate has been below 800 g/d the effects of increasing feeding intensity on milk production has been more variable ( Figure 5). Results from the study of Peri et al. (1993) are inconsistent with other studies. In the former study the heifers were fed to gain either 625 g/d (A), 708 g/d (B), or 1100 g/d (C) from 6 to 10 months of age. ...
Mäntysaari, P. 2001.Effect of feeding before puberty and during gestation on milk production potential andbody development of dairy replacement heifers. University of Helsinki, Department ofAnimal Science. Publications 60. 44p. + 5 encl.
ABSTRACT
This thesis consists of studies concerning the effect of feeding before puberty and duringgestation on pre-pubertal mammary growth, subsequent milk yield and body development ofreplacement heifers. Publications I and II investigated the effect of high (daily gain 850 g) orlow (daily gain 650 g) levels of feeding with urea or rapeseed meal as protein supplements ongrowth and mammary development of pre-pubertal Finnish Ayrshire heifers. It was shownthat heifers on the high feeding level had less mammary parenchymal tissue compared withheifers fed lower levels of feeding. The amount of mammary parenchymal tissue waspositively correlated with plasma growth hormone (GH), but not plasma IGF-Iconcentrations. Furthermore, no correlation existed between plasma GH and IGF-Iconcentrations. On a high feeding level Finnish Ayrshire heifers under 220 kg live weight hada higher growth rate when rapeseed meal rather than urea was used as protein supplement ona hay-barley based diet. For pre-pubertal slaughter heifers it appears that urea is not suitablesource of supplementary nitrogen for hay and barley based diets. Instead, protein source hadno effect on pre-pubertal mammogenesis at either feeding level.The effect of feeding intensity during gestation on subsequent milk yield was investigated inpublication IV. It was shown that during the first six months of gestation daily gains of 800 g,or higher, had no effect on subsequent milk yield but resulted in greater fat deposition andreduced postpartum intake potential. On the other hand, during the last trimester a high levelof feeding (live weight change over 800 g/d) was advantageous in attaining maximal milkproduction.The effect of feeding on body development of pre-pubertal (publications I and III) andpregnant heifers (publication IV) was examined. It was observed that pre-pubertal heifers fedon a low level of feeding had higher wither heights at puberty than heifers fed moreintensively. Results suggest that pre-pubertal wither height is determined more by age thanlive weight. Heart girth was shown to be a good predictor of pre-pubertal live weight. Duringpregnancy high (gain 800 g/d) compared with moderate (gain 650 g/d) planes of nutrition hadno effect on body size (wither height, body length) but increased heart girth, hip width andbody condition score of primiparous cows at parturition.Live weight at parturition and daily gain before and after breeding had positive geneticcorrelations with first lactation milk yield within field data reported in publication V.Therefore, it appears that genetic selection for higher milk production will gradually lead tohigher genetic growth potential. Such changes need to be taken into account in futurerecommendations of daily gain acceptable for pre-pubertal dairy replacement heifers.Based on the current studies it was suggested that for pre-pubertal Finnish Ayrshire heifersdaily gains above 650 to 700 g have detrimental effects on pre-pubertal mammogenesis.Dietary protein source has no effect on mammary growth. During the first six months ofgestation a moderate feeding level is recommended to avoid excessive fat deposition andensure maximal postpartum intake. However, during the last trimester intensive feeding isnecessary in attaining maximal milk production.
Effect of feeding before puberty and during gestation on milk production potential and body development of dairy replacement heifers. Available from: https://www.researchgate.net/publication/47932245_Effect_of_feeding_before_puberty_and_during_gestation_on_milk_production_potential_and_body_development_of_dairy_replacement_heifers [accessed Mar 02 2018].
Purpose
This article reviews the importance of feed efficiency in heifer rearing and discusses potential factors that can modulate feed efficiency and their possible implications in future performance and economics of heifer rearing.
Sources
Herein, we have gathered historical data from the largest contract heifer operation in Europe (Rancho Las Nieves, Mallén, Spain) to describe feed efficiency and economic returns throughout the rearing process. We have also compiled results from peer-review literature.
Synthesis
Heifers represent the sustainability and future of the herd and are responsible for important economic costs as well as a considerable environmental impact. Factors influencing feed efficiency include age, type of ration fed, and environmental conditions. Feed efficiency is ~50% during the first 2 mo and progressively declines to ~7% before calving. Also, feed efficiency is affected by stocking density, physiological status of the animals, and diet nutrient composition, including the ratio between CP and ME.
Conclusions and Applications
Regularly measuring feed intake and BW in dairy replacements is pivotal to improve heifer effectiveness and economics. Considering both, feed costs and feed efficiency, the most economically advantageous stage to foster body accretion in heifers is right after weaning until about 200 d of life. In addition, growth after weaning is positively correlated with future milking performance. Providing excessive amounts of forage after weaning should be avoided. Last, restricting the amount of diet fed to heifers, while maintaining an adequate supply of nutrients, may increase dietary unit costs and total daily feed costs.
A high plane of nutrition fed prior to puberty has been shown to negatively affect mammary gland development in heifers by decreasing secretory tissue and increasing adipose tissue (Sejrsen et al.,1982; Stelwagen and Grieve, 1990). Heifers reared on a high plane of nutrition have been shown to have depressed milk yields throughout their productive lives (Peri et al., 1992). Presently, it is not known why a high plane of nutrition inhibits mammary parenchymal development. Hormones and local growth factors play an important role in mammary gland development (Plaut, 1993). It is possible that a high plane of nutrition alters levels of hormones or growth factors that are needed for parenchymal development. Because heifers take up to 10 months to reach puberty, research in this area has been limited. Goats reach puberty 3–5 months sooner than heifers, therefore a similar study of caprine mammary development could be carried out in almost half the time. This study was conducted to test the usefulness of goats for such studies, and to test if a high plane of nutrition affects prepubertal mammary development.
Feeding proteins that contain higher levels of undegradable protein may optimize amino acid amount and quality in the small intestine and result in lower environmental nutrient losses. Research was designed to determine the influence of proteins high in undegradability in diets low in CP. Three experiments were conducted comparing nitrogen metabolism, diet digestibility, and gain. In Experiment 1, 14 growing lambs (23.5 kg) were allotted to a 2 × 2 factorial arrangement of treatments. Lambs fed a diet low in CP gained faster (0.15 kg/d vs 0.12 kg/d, P>0.30) when receiving part of the dietary CP as fish meal (a source high in undegradable protein) as compared to soybean meal (a source low in undegradable protein). Experiment 2 compared digestibility and nitrogen retention when 11 growing lambs were fed low protein diets (10% CP) containing either soybean meal or fish meal, or a 17% CP soybean meal control. Nitrogen retention was greater in lambs receiving fish meal (0.76 vs –1.0 g/d) than those receiving soybean meal (P<0.05). The lambs on the fish meal treatment also had lower urinary nitrogen excretion (P<0.05) than lambs receiving soybean meal diets. In Experiment 3, 11 wethers were allotted to three treatments containing 10% CP, 10% CP plus the ionophore Bovatec®, or a control containing 13% CP in the feed. The presence of the ionophore lowered nitrogen retention (P<0.05) when compared to the other low protein diet. The presence of a protein source high in undegradability resulted in improved nitrogen metabolism and reduced the amount of nitrogen excretion, whereas the addition of an ionophore resulted in no improvements in nitrogen metabolism.
Limit-feeding high-concentrate or high-digestibility diets for growing dairy heifers may offer an economical alternative to ad libitum consumption of the high-forage, low-digestibility diets that are traditionally fed to dairy heifers. Literature pertaining to economic, physiological, and nutritional responses to alterations in feeding level and dietary concentrate level are reviewed. From the available research, it was found that limit-feeding higher-concentrate diets did not affect growth or first-lactation milk production compared with feeding high-forage diets when equivalent levels of gain are obtained. Dairy heifers that are limit-fed often have greater diet digestibility, lower levels of environmental excretion and methane production, and greater feed efficiency. Although the digestibility was increased for heifers limit-fed high-concentrate diets, retention and excretion of N was not consistently affected. It was concluded that limit-feeding high-concentrate diets does not need to be excluded as a management option and may offer an opportunity for heifer growers to reduce feed costs and environmental output under the circumstances thus far investigated.
Thirty-three heifers were assigned to 3 analogous groups of 11 animals each in which three different levels of feeding were used from 6.5 to 10 months (first period) and from 11 to 12 months of age (second period): the feeding level recommended by the IZ-INRA system (1997) (group C), lower and then 20% higher in subsequent periods in relation to group C (group D), and 20% higher in both periods in relation to group C (group H). Body weight gains in different rearing periods were assumed as follows (g/day): 700 (C), 560 and 840 (D), 840 (H), and from 13 months of age to 3 weeks before calving 700 g/day in all the groups. Next the heifers were fed the rations specified for primiparous cows assuming maximum production at peak of lactation to be 35 kg milk per day. The varying level (group D) of feeding prepubertal and postpubertal heifers was found to have no adverse effect on ovarian size and status at 12 months of age and on subsequent growth and development of these animals, while having a beneficial effect on their milk performance during the first lactation. The high feeding level (group H) from 6.5 to 12 months of age led to increased daily weight gains and accelerated the date of reproductive performance of heifers compared with their age-mates from group C.
The study investigated intense feeding of Black and White heifers (with a high Holstein-Friesian inheritance) during sexual maturation and its effects on the size and morphological structure of ovaries at 12 months of age as well as selected reproductive performance traits. At 6 months old, 33 heifers were assigned to three equal groups of 11 animals each. Three feeding levels were applied from 6 to 10 months (first period) and from 11 to 12 months of age (second period): in group K (control), the level recommended by IZ-INRA standards (2001) for a weight gain of 700 g/day; in group D, a level of 20% lower than in the first period and 20% higher than in group K; in group W, a 20% higher level in both periods than in group K. From 13 months of age to 3 weeks before calving, all the heifers were fed to achieve a weight gain of 700 g/day. The chemical composition of the feed, growth rate, and selected parameters of reproductive performance were recorded both in the heifers and primiparous cows. The size and morphological structure of the ovaries were determined using ultrasonograph at 12 months of age. The results obtained indicate that, when compared to Polish IZ-INRA standards, ovarian size and morphological structure at 12 months of age, subsequent reproductive performance and growth rate of BW′HF heifers were not adversely affected by modifying their feeding during sexual maturation.
Twenty-two buffalo heifers, 6-8 months old, 98.57±5 kg average body weight were divided into two groups and randomly assigned either control diet for the duration of the experiment which contained 2.55 Mcal/kg of DM (as per NRC, 2001 recommendations of Holstein heifers) or a stair-step diet which contained 2.03 Mcal/kg of DM (80% ME of control-SLE) fed for 120 days followed by 3.01 Mcal/kg of DM (120% ME of control-SHE) for 60 days. Heifers on SLE diet gained (p<0.05) less weight (0.51 vs. 0.60 kg/day) but on SHE diet, gained significantly (p<0.01) more weight (0.82 vs. 0.58 kg/day) respectively, compared to heifers fed the control diet. Heifers on the SLE diet have poorer FCR (6.73 vs 5.72) but with SHE diet have better (p<0.01) FCR (5.23 vs 7.41) compared to control, respectively. Daily DM consumption for the entire feeding period was similar in both groups but heifers reared on stair-step scheme gained 1.67% higher weights than control. Blood was collected on 0, 120 and 180 days of the experiment and showed that all haematological values increased with the advancement of age, with the exception of lymphocyte percentage; however, these values were not affected by dietary treatment. Apparent digestibility of DM, OM and CP remained unchanged on both the SLE and SHE diets, respectively, compared to the control. However, NDF and ADF digestibility increased (p<0.05) with the SLE diet but decreased with the SHE diet compared to control diet, respectively. Nitrogen retention was not affected in heifers fed either the SLE or SHE diets compared to the control (p>0.05). Feed costs per kg gain of heifers fed stair-step diets were 16.57% less than those fed the control diet.
Seventy high genetic merit Holstein heifers were used in two experiments to investigate (1) the effects of plane of nutrition and diet type during the pre-pubertal period and (2) the effects of plane of nutrition during the postpubertal period on metabolic hormone concentrations, growth and milk production. In experiment 1, treatment 1 and 2 heifers were given food to achieve a live-weight gain of 0.70 and 0.95 kg/day from 3 to 10 months of age on a grass silage based diet, while treatment 3 heifers were given food to achieve 0.95 kg/day on a barley straw/ concentrate diet. During the pre-pubertal period, heifers reared on treatment 1 had significantly higher growth hormone·(GH) concentrations (ng/ml per 1 h) than heifers reared on treatment 2 (P < 0.01) and had significantly lower insulin concentrations than heifers reared on treatment 3 (P < 0.01). Heifers reared on treatment 1 had significantly lower insulin-like growth factor 1 (IGF-1) concentrations than those reared on treatment 3 (P < 0.01). At 10 months of age heifers reared on treatment 1 were of lower condition score (P < 0.01) than those on treatment 2 and had a smaller heart girth diameter (P < 0.01) than those on treatments 2 and 3. During the first lactation, milk yield and composition produced by the heifers was not significantly affected by treatment. In experiment 2, treatment A heifers were given, from 14 to 24 months of age, a low plane of nutrition to allow a live-weight gain of 0.65 kg/day on a grass silage and grass based diet during the winter and summer periods respectively. Treatment B heifers were kept on a high plane of nutrition to allow a liveweight gain of 0.90 kg/day on the same forage along with concentrate supplementation. During the rearing period, GH and IGF-1 concentrations were not significantly affected by treatment. Treatment A heifers weighed less before calving (P < 0.05), had a lower condition score (P < 0.01), and had a smaller heart girth diameter (P < 0.01) than those on treatment B. During the first 10 weeks of lactation, heifers on treatment A had a higher silage dry matter intake and lost less weight (P < 0.05) than those on treatment B, however, by 20 weeks of lactation these effects had disappeared. Milk yield and composition during the first lactation were not significantly affected by treatment. Overall, the findings of experiments 1 and 2 did not show any beneficial effects of higher weights at first calving in high genetic merit Holsteins and therefore indicate that accelerated growth in the pre- or post-pubertal period may not be required.
Twenty two weaned heifers about 6-8 months old and 98.57±5 kg average BW were divided into two groups; either fed continuously as per NRC recommendations (control) or stair-step nutritional regimen (SSNR). For control group total mixed rations were formulated by adapting the large dairy breeds heifer's nutrient requirements for growth rate of 0.6 kg/day considering body weight of 100, 200 and 300 kg at the beginning of phase I (from 8 to 13 months), phase II (from 14 to 19 months) and phase III (from 20 to 25 months), respectively. The SSNR group, in each phase started on restricted energy diet (80% ME of control) for 4 months and ended with compensatory energy (120% ME of control) for 2 months. There was no difference in daily DMI, weight gain and FCR in heifers raised on SSNR versus control diet. One heifer from each group had retarded growth, and was excluded from reproductive studies. Proportion of heifers attaining puberty by 18-23 months of age did not differ (P>0.05) between SSNR (80%) and control group (70%). Pubertal age (649±21.76 vs 639±21.46 days) and BW (382±14.00 vs 364±12.48 kg) were not affected by SSNR compared to control diet. Similarly, differences in services per conception or conception rate between the two groups were nonsignificant. However, SSNR reduced feed cost by Rs 16.69/kg BW gain compared to control. It can thus be concluded that SSNR shows economic advantage in rearing of buffalo heifers from post-weaning to conception age without any negative effect on reproductive efficiency compared with heifers fed as per NRC recommendations.
The effect of feeding level and nitrogen source on mammary development and plasma hormone levels of pre-pubertal (86 to 220 kg) Finnish Ayrshire heifers was studied. The treatments were: (1) LU, low feeding level + urea; (2) LR, low feeding level + rapeseed meal; (3) HU, high feeding level + urea; (4) HR, high feeding level + rapeseed meal. The average daily gains of the heifers on LU, LR, HU and HR diets were 692, 655, 805 and 890 g, respectively. There was a significantly higher amount of mammary parenchymal tissue and parenchymal DNA at low (L) compared with high (H) feeding levels, but no difference in mammary weights between nitrogen sources was found. Plasma insulin concentration was greater at H compared with L feeding levels, but plasma growth hormone (GH), insulin-like growth factor-I (IGF-I) and prolactin concentrations were not significantly affected by the feeding level. The amount of mammary parenchymal tissue did not correlate with the mean plasma concentration of prolactin and insulin. Also, no significant correlation between plasma GH (r = 0.32; P < 0.15) or IGF-I (r = 0.37; P < 0.09) and mammary growth was found. However, when GH measurements around feeding (2 h) were excluded, mammary development was positively correlated to plasma GH (r = 0.44; P < 0.05).
The effect of pre- and post-puberty feeding of rations diversified in terms of energy and protein content on the growth rate, body condition, fatness, milk yield and reproduction efficiency of Simmental heifers was investigated. The experiment was carried out on 40 Simmental heifers from 6 months of age to day 100 of lactation, allotted to 5 groups according to age and body weight. During pre- (from 6 to 11 months of age) and post-puberty (from 12 to 13 months of age) the animals were fed rations of different or the same levels of energy (UFL) and protein (PDI) as the control Group K, which was fed according to IZ-INRA (2001). The respective levels of UFL and PDJ in the rations for the experimental groups in both periods were, % of control Group K : Group A, 85/85 and 115/115; Group B, 85/115 and 100/100; Group C, 115/85 and 100/100; Group D, 115/115 and 115/ 115. From 14 months of age to day 100 of lactation the animals of all groups were fed the same as the control group. Heifers that received higher UFL and lower BTJ (Group C) or increased levels of energy and protein (Group D) in their pre-puberty rations than the control group, at 11-18 months of age and in the period from 6 months of age to calving, achieved higher body weight gain than the animals of the remaining groups (P0.05) than animals in other groups. Total milk production per cow in Groups A and B was about 11% higher than in Groups K and D, and about 6% higher than in Group C, but the differences were not statistically significant (P>0.05). Independently
Twenty-one 6-month-old Israeli Holstein heifers were used to determine the effect of three 6-month feeding regimes on growth, blood concentration of insulin, prolactin and insulin-like growth factor-1 (IGF-1), attainment of puberty and milk production during first lactation. Feeding regimes were as follows. (1) Restricted: the heifers were given food during months 1, 2 and 4, 5 of an experimental period, to support live-weight (LW) gain of 0·35 and 0·50 kg/day, respectively and during months 3 and 6 the heifers were given food to support compensatory growth. (2) Control: the heifers were given food to support LW gain of 1·0 kg/day. (3) Control + C: the heifers were given the same as the control, with a daily supplement of 0·05 mg/kg LW cimaterol (C) for 4 months. The total LW gain of the restricted heifers during the 6 months of the trial was significantly lower than that of the control heifers. Cimaterol improved growth rate only during the first 2 months of its application and its withdrawal was associated with severe LW gain retardation. The feeding regime employed in the restricted treatment was associated with a significant reduction in serum concentrations of insulin, prolactin and IGF-1 during the first restricted phase, followed by an elevation in the first compensatory phase. During the second restriction-compensation cycle, only the serum concentration of prolactin was significantly reduced. Cimaterol addition was also associated with a reduced blood concentration of the hormones. The animals in the restricted, control and control + C groups attained puberty at LW of 249·2, 277·6 and 304·9 kg (P <0·05), respectively. No effect of the treatments on milk yield was observed. The effect of the feeding regimes on skeletal growth and on metubolizable energy efficiency for growth is discussed.
Two-hundred and fifty-four crossbred gilts were allotted to 'moderate' or 'control' growth regimens from 9 to 25 weeks of age. The moderate regimen used dietary fiber to achieve alternating phases of moderate and maximum growth during four distinct pre-pubertal periods. High-fiber diets, containing 35% ground sunflower hulls, were fed during periods one and three (3 and 5 weeks, respectively) to slow growth. During periods two and four, low-fiber corn–soybean meal (CSBM)-based diets were fed for 3 and 5 weeks, respectively, to maximize growth. Control gilts were fed CSBM-based diets in all periods to maximize growth. Ad-libitum access to feed was allowed at all times with both regimens. After 25 weeks of age, both treatment groups were managed similarly. Analysis of mammary tissue collected on day 110 of gestation revealed that moderate gilts had less (P 5 0.03) parenchymal tissue, and tended to have less (P 5 0.09) total DNA than control gilts. However, during lactation moderate females consumed more feed (P 5 0.02) and tended (P 5 0.07) to wean heavier litters. Altering gilt growth before puberty enhanced sow lactation performance despite decreasing pre-lactation mammary development. © 2001 Elsevier Science B. V. All rights reserved.
A field study was conducted to study the relationships between average daily gain (ADG) of heifers and their first lactation milk yield. To predict the body weight (BW) the heart girth of 4058 heifers was measured by AI-technicians. Based on these measurements and national milk recording data, the ADGs before and after breeding were calculated. Other variables collected were after calving BW, calving age, and milk production yields on first lactation. After edits the final data included 2194 Ayrshire (Ay) and 738 Friesian (Fr) heifers and their 7215 relatives. Data used for calving BW and ADGs after breeding was 43% smaller because of missing information. The average BW and age at breeding were 356 kg and 483 days for Ay and 376 kg and 484 days for Fr, respectively. The after calving BW for Ay was 502 kg and for Fr 520 kg. The weights correspond to ADGs of 660 g (S.D. 99 g) and 695 g (S.D. 114 g) before breeding, and 497 g (S.D. 190 g) and 492 g (S.D. 196 g) after breeding for Ay and Fr breeds, respectively. The average 305-day milk yield for Ay was 6198 kg and for Fr 6440 kg. Positive genetic correlations between growth rate before (0.13±0.11) and after (0.34±0.17) breeding and milk yield as well as calving BW and milk yield (0.26±0.13) were found. The environmental correlation between ADG before breeding and milk yield was positive (0.13±0.04), while the ADG after breeding and milk yield was uncorrelated (−0.01±0.04). Based on the feeding trials a negative environmental correlation between ADG before breeding and milk yield could have been expected. It was concluded that the negative effect could not be estimated, because of the disturbance caused by herd effect. Also, the fact that most of the heifers had been reared within recommended limits of ADG could have affected the results.
Six-month-old Israeli Holstein heifers were fed on a low-energy (LE) diet with corn straw as the main feed component during the 4 months of summer, followed by a high-energy, high-protein diet for compensatory growth during the 2 months of autumn. During the same period a control group was fed to support an average daily gain of 0.65 kg. During the LE phase, the mean daily gains in heart girth, body weight and hip height were 51 to 67% lower than those of the control group. During the compensatory phase, mean daily gains in body weight, hip height and heart girth group were 197 to 225% times greater than in the control group. By the end of the compensatory phase the experimental group had the same mean body weight as the control group, but the mean hip height of the heifers was 2 cm shorter. Puberty was attained by the experimental group one month later than in the control group, but at the same body weight. Milk production was similar in the two groups. The efficiency of the metabolisable energy intake for body weight gain in both treatments was discussed.
The effects of body weight (BW) gain, different sources of protein during the prepubertal period (90 to 320 kg of BW), and the performance of Holstein heifers during their first lactation were studied. Heifers (n = 273) were assigned to one of three dietary energy treatments that were designed to achieve average daily gains of 0.6, 0.8, and 1.0 kg/d. Within each energy treatment, different protein sources (plant protein and urea or both plant and animal proteins) were imposed. Actual average daily gains by heifers on each energy treatment were 0.68, 0.83, and 0.94 kg/d for heifers that were fed diets formulated for average daily gains of 0.6, 0.8, and 1.0 kg/d, respectively, which allowed the following ages at first calving: 24.5, 22.0, and 21.3 mo. Breeding was initiated when heifers weighed approximately 340 kg. Protein sources did not affect average daily gain or milk yield. Analysis of the preplanned comparisons of actual 305-d and 4% fat-corrected milk yields indicated that yield was significantly reduced for heifers grown at 0.94 kg/d (9387 and 8558 kg, respectively) compared with that of heifers grown at 0.68 kg/d (9873 and 9008 kg, respectively). However, further regression analysis of fat-corrected milk and residual milk from a test day model on prepubertal BW gain only explained 8 and 2% of the variation in milk yield, respectively. Postcalving BW and body condition score were different among treatments. Posttreatment factors, such as postcalving BW, accounted for more of the variation in milk yield than did prepubertal BW gain. Prepubertal BW gains, when evaluated on a continuum from 0.5 to 1.1 kg/d, explained little of the variation in milk yield; therefore, BW gain during the prepubertal period did not significantly affect milk yield during first lactation.
This research examined the extent to which dietary energy restriction modulates growth and mammary tissue composition during different developmental stages. Female rats were assigned to the following three dietary treatments: 1) ad libitum access to feed (AL), 2) 30% continuous energy restriction (CER), and 3) stair-step energy restriction (SSER). The SSER treatment consisted of an 8-wk, alternating schedule beginning with 60% energy restriction for 2 wk, followed by realimentation to feed offered for ad libitum intake for 2 wk. All treatments were initiated when rats were 5 wk of age. After the stair-step regimen, SSER rats were maintained on a 30% energy-restricted diet for the duration of the experimental period (25 wk of age). Rats reared on the energy restriction regimens weighed less and consumed less (P < .05) feed than controls, but they had feed efficiencies similar to those of controls. Energy restriction delayed the onset of puberty and retarded the growth of the offspring but had no effect on litter size. The overall values (averaged pregnancy through involution stages) of DNA, RNA, and RNA: DNA ratio (based on fat-free DM) and protein concentrations were similar in the mammary tissues of the energy restriction groups and those of the AL group. Lipid content in mammary tissue was generally decreased in the CER and SSER groups compared with the AL group. In summary, energy restriction delayed the onset of puberty and retarded the growth of the dam and progeny, but it did not affect mammary cellularity as it reduced fat deposition in the mammary gland.
One hundred-sixteen Holstein heifers (mean BW, 175 kg) were randomly assigned to diets of alfalfa silage or corn silage and were fed to gain approximately 725 or 950 g/d in order to study the influence of prepubertal diet and rate of gain on mammary growth and milk production. Blood was collected before puberty for hormone determination, and 8 heifers per group were killed at puberty for evaluation of tissue variables. Serum growth hormone was reduced, and IGF-I was increased, in the group of heifers reared at a high rate of gain on the corn silage diet. Accompanying the decline in growth hormone, total mammary parenchymal DNA and RNA was reduced in heifers reared at a high rate of gain on the corn silage diet. Mammary parenchyma in heifers of the latter group contained a greater volume of adipocytes and a lower volume of epithelial cells than did mammary parenchyma in heifers of other groups. Data are consistent with previous investigations that showed a deleterious effect of prepubertal rapid weight gain on mammogenesis when accompanied by excess body fat deposition. However, this effect did not cause a decline in subsequent milk production.
Ten French Alpine kids were used to determine whether mammary development was altered by level of nutrient intake during the prepubertal period. At 6 wk of age, kids were paired on the basis of BW and assigned to an ad libitum or restricted diet of milk from Jersey cows. Kids on the restricted diet were fed 70% of their pair mate's milk intake for 4 wk and then 50% for 9 wk. Low quality grass hay was available for all kids. The ADG was greater for kids fed for ad libitum intake. Kids fed for ad libitum intake had larger mammary glands and increased adipose deposition. Measurement of hydroxyproline indicated that connective tissue increased with gland size. Kids on the restricted diet had more DNA and protein per gram of mammary gland, indicating greater secretory development. Goats can be used as a model to study the effect of level of nutrient intake on hormones and growth factors that regulate mammary gland development.
Effects of concentrate source (corn or soybean hulls) and amount (40 or 80% of DMI) on plasma hormone concentrations were evaluated for 32 prepubertal Holstein heifers in a 2 x 2 factorial design. Blood samples were collected every other day from d -4 through d 28 of the experiment and were analyzed for growth hormone, prolactin, IGF-1, and glucose. Ruminal samples were collected by esophageal tube on d 0, 7, 14, 21, and 28 and were analyzed for VFA content. Serial blood samples were collected on either d 25 or 26 at 20-min intervals for 8 h and were used for profile analysis of growth hormone and prolactin. Heifers fed 80% concentrate had higher IGF-1 concentrations in serum (158.1 vs. 131.9 ng/ml) than did heifers fed 40% concentrate, and heifers fed corn tended to have higher IGF-1 concentrations than heifers fed soybean hulls. Prolactin concentrations in samples that were collected every other day were higher for heifers fed the 80% soybean hull diet than for those fed 40% concentrate diets or the 80% corn diet. Effects of source and amount of concentrate on plasma prolactin concentrations were not evident in serial samples. Concentrate source or amount had no effect on plasma growth hormone or glucose. At high concentrate intakes, the source (soybean hulls vs. corn) affected intake parameters, ruminal VFA content, and prolactin concentrations.
Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)
High-level production of a growth promoting peptide hormone somatomedin C (insulin-like growth factor I) has been achieved using recombinant DNA techniques in Escherichia coli. We found a new structural protein, designated as LH, to stabilize somatomedin C in vivo, and constructed expression vectors for somatomedin C fusing to LH through a methionine and through a tryptophan, respectively. Each of the fused proteins was produced at approximately 4.5 X 10(5) molecules per single E. coli cell and comprised more than 20% of the total cellular proteins. Somatomedin C was obtained in high yield by limited cyanogen bromide degradation of the methionine-type fused protein, in spite of somatomedin C itself having a Met at the 59th position, followed by renaturation of the resultant reduced peptide. The tryptophan-type fused protein was also converted to the peptide hormone by treating with 3-bromo-2-nitrophenylsulphenyl skatole or N-chlorosuccinimide. The recombinant somatomedin C obtained by these procedures was identical with the native one in amino acid sequence as well as in biological activity of stimulation of DNA synthesis in BALB/c 3T3 cells.
The primary objective of this study was to improve the productive efficiency of growth via optimal use of both high fiber-low quality and high energy-high protein feeds in diets for growing dairy cattle. Twenty Holstein heifers were randomly assigned to either a control or treatment group. The control diet met the National Research Council (NRC) requirement for .45 kg/d gain, with heifers calving at 24 to 26 mo of age. The test groups were fed according to a 5-2-5-2 mo schedule in which the nutrient density was alternately 15% below or 40% above the NRC requirement. Results showed that the heifers on the test dietary regimen (compensatory growth) gained more and consumed less, resulting in significantly improved efficiency of growth (body gain/dry matter intake X 100), energy (body gain X 1,000/metabolizable energy (ME) intake) and protein utilization (body gain/protein intake X 100) in comparison to control animals (13.0 vs 7.3%; 57.9 vs 32.6 g/Mcal ME; 96.5 vs 54.2%, respectively). Marked changes in average concentration of urea-N, glucose, triglycerides, cholesterol and lecithin cholesterol acyltransferase activity in blood were seen for test heifers during the stair-step growth phase (i.e., alternating maintenance and compensatory). Evidence from this experiment suggests that the phased growth (stair-step) system offers a simple, practical and cost-effective method for raising dairy heifers.
Roles of the lactogenic hormones prolactin and placental lactogen in mammary development in ruminants were reviewed. In contrast with other ruminants, failure to detect lactogenic activity in the serum of pregnant cows (in excess of that attributed to prolactin) suggests that placental lactogen may have little direct effect on mammary growth or lactogenesis. However, replacement and ablation experiments using ergocryptine provide definitive evidence that increased periparturient secretion of prolactin is necessary for maximal milk production in cattle. Quantitative microscopy indicates a relative failure of mammary cells in cows with inhibited secretion of prolactin to differentiate structurally. Prolactin induces synthesis and secretion of alpha-lactalbumin in prepartum bovine mammary tissue. Temporary disruption of mammary microtubules immediately prepartum in pregnant heifers reduced subsequent milk production, biosynthetic capacity, and cellular differentiation. For maximal milk production, mammary secretory cells apparently must respond to lactogenic hormone stimulation during the immediate periparturient period. Colchicine may desensitize the mammary epithelium to prolactin action. Membrane binding of radiolabeled human growth hormone to ruminant mammary gland provides a measure of lactogenic hormone binding sites. Specific binding to 600 micrograms of mammary membrane protein was 296% greater in lactating, compared with nonlactating, pregnant (65 days of gestation) ewes. Binding capacity (fmol/mg membrane protein) averaged 275 +/- 57 in mammary membranes from nonlactating, pregnant ewes (100 days gestation, n = 2) and 2,325 +/- 521 in mammary membranes from lactating ewes (n = 6, 14 to 21 days postpartum). Greater understanding of hormonal regulation of the ruminant mammary gland likely will result in development of techniques to produce milk more efficiently and perhaps capability to evaluate production potential of young animals.
Twenty prepubertal heifers (averaging 155 kg body weight) were assigned to one of four treatment groups in an experiment of 2 X 2 factorial design. The main effects were photoperiods of 8 h light:16 h dark (8L:16D) vs 16L:8D, and LOW vs HIGH plane of nutrition. Heifers on the LOW plane of nutrition were fed to achieve a growth rate of approximately .7 kg/d; daily feed intake was restricted with no orts and was identical in both groups of heifers subjected to either 8 or 16 h of light daily. Heifers on the HIGH plane of nutrition were fed ad libitum to achieve a growth rate greater than 1 kg/d. All heifers were slaughtered during the luteal phase of an estrous cycle at an average body weight of 337, 334, 360 and 349 kg for 8L:16D-LOW plane, 16L:8D-LOW plane, 8L:16D-HIGH plane and 16L:8D-HIGH plane groups, respectively. Average time on treatment was 233, 236, 206 and 181 d and average estimated carcass weight gain was .39, .40, .55 and .61 kg/d, respectively. Within LOW or HIGH planes of nutrition, photoperiod did not affect live body weight gains. A photoperiod of 16L:8D, compared with 8L:16D, increased protein content in the 9-10-11th rib section of heifers on HIGH nutrition (16.2 vs 14.6%), but not in heifers fed the LOW plane of nutrition (15.5 vs 16.1%). However, within 8L:16D groups, HIGH plane reduced rib section protein content as compared with LOW plane of nutrition (14.6 vs 16.1%); there was no difference observed within 16L:8D groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Mammary glands are enzymatically dissociated and the resulting tissue digest enriched for epithelial cells by isopycnic banding on a density gradient of Percoll. The cells are embedded within a rat tail collagen gel matrix and fed with the appropriate medium. Growth and differentiation are superior in such a system when compared to culture on plastic, using identical media.
Membrane preparations and Triton X-100 solubilized fractions from the mammary gland and liver of the lactating dairy cow were capable of specific binding of [125I]hGH and [125I]oPRL. The specific binding of the latter was significantly lower and could not be increased by higher receptor levels. Displacement studies of [125I]hGh by hGH, bPRL and oPRL revealed that the two latter hormones have a 20–40-fold lower affinity for the receptor than hGH, although strong indications exist that they all bind or the same sites. This feature is unique for cows and does not exist or is much less pronounced in rodents.
Ovine GH (oGH) was determined by homologous RIA on 118 samples from 45 chronically catheterized ovine fetuses from 66 days of gestation to term (147 days). A triphasic pattern of oGH concentration was demonstrated with high circulating GH concentrations (148.0±9.6 ng/ml) at 60-70 days gestation, falling by 100-110 days (49.0±7.3 ng/ml), increasing again to peak at 130-140 days (150.4±10.5 ng/ml), and again decreasing to lower concentrations characteristic of the neonate before delivery. In samples obtained during fetal surgery (n=63), a similar pattern was observed, but after 120 days of gestation, 15 of 36 plasma oGH values were above the upper limit of the normal range calculated from the chronic group. Similar findings were observed in 42 samples from fetuses that had developed hypoxia or acidosis, suggesting that stress-related GH release develops in late gestation. Maternal GH concentrations did not correlate with gestational age and were low throughout pregnancy (4.4±0.7 ng/ml). The pattern of GH in the ovine fetus is compared to that of the human fetus. In both species, high fetal GH concentrations were noted in midgestation, followed by a subsequent fall in plasma GH; however, in the sheep, in contrast to the human, a second peak of plasma GH was noted in late gestation. It is postulated that in both species, the changing pattern of fetal plasma GH represents different stages in the development of hypothalamic regulation of the fetal pituitary.
Insulin-like growth factors (IGFs) I and II (IGF-I, IGF-II) and Des-3-IGF-I at physiological concentrations are potent mitogens of bovine undifferentiated mammary epithelial cells cultured in collagen in a serum-free medium. Des-3-IGF-I was found to be as potent as IGF-I, while IGF-II was significantly less active. All three factors acted either synergistically or additively with epidermal growth factor (EGF), cholera toxin and fetal calf serum (FCS). Indirect evidence indicates that despite its lower mitogenic activity the action of IGF-II is mediated through IGF-I receptors. The galactopoietic activity of Des-3-IGF-I and IGF-II was studied in an organ culture of bovine lactating mammary glands using lactogen-responsive fat synthesis as a test. Neither Des-3-IGF-I nor IGF-II exhibited galactopoietic activity nor did they affect the galactopoietic activity of prolactin.
Bovine mammary undifferentiated epithelial cells from young female calves, cultured in three-dimensional collagen gels in serum-free medium exhibited ultrastructural organization that resembled the in vivo situation. Extracts of bovine pituitary, kidney, uterus and mammary gland, stimulated cell proliferation in a dose-dependent manner. This mitogenic activity strongly synergised with the existant growth factors (GFs) in FCS and with IGF-I, while the addition of EGF had only minor effect. No synergistic manifestation was found with cholera toxin but pertussis toxin inhibited the growth-promoting activity of all four extracts. Other experiments indicated that this mitogenic activity does not result from prolactin, growth hormone or fibroblast growth factor. The present and former results, in which synergism between IGF-I and cholera toxin was demonstrated, suggest therefore, that the mitogenesis of normal mammary epithelial cells regulated by several tissue derived growth factors, consists of at least two pathways which are distinct from those activated by EGF and IGF-I. One of these pathways indicates involvement of pertussis toxin-sensitive GTP-binding proteins, and the other, activation of cholera toxin-sensitive adenylate cyclase.
Plasma GH profiles and circulating concentrations of plasma insulin-like growth factors-I and -II (IGF-I and -II) were examined in 20 steers on either high (3% dry matter of body weight per day) or low (1% dry matter of body weight per day) planes of nutrition with or without an implant of oestradiol-17β. The response of plasma IGF-I and -II to a bolus injection of bovine GH (bGH) was also investigated.
Reduced feeding significantly ( P <0·01) increased the mean concentration, peak height and integrated area of plasma GH. Treatment of steers with oestradiol at low nutrition significantly increased baseline GH concentrations. Treatment of steers with oestradiol at high nutrition significantly ( P <0·05) increased mean, baseline, peak height, and integrated area of plasma GH. GH pulse frequency was not changed by either nutritional plane or oestradiol treatment.
Basal concentrations of plasma IGF-I were significantly ( P <0·01) decreased by reduced feeding in both the oestradiol-treated and the control group. Treatment with oestradiol increased ( P <0·01) basal plasma concentrations of IGF-I at both high and low levels of nutrition. After i.v. injection of bGH (0·1 mg/kg body weight), an increase in plasma IGF-I was observed only in steers at high nutrition. Basal concentrations of plasma IGF-II were not altered by nutritional manipulations but were significantly ( P <0·001) increased by oestradiol treatment. After bGH infusion only steers at high nutrition showed an increase in plasma IGF-II. Significant correlations were observed between daily body weight gain and plasma concentrations of IGF-I ( r = 0·91, P <0·001, n = 20) and also between the capacity of the high-affinity hepatic somatotrophic receptor and plasma IGF-I ( r = 0·89, P <0·001, n= 10).
Decreased plasma concentrations of IGF-I at a low level of nutrition may abolish the growth-promoting activity of circulating GH. The increase in both GH secretion and the number of somatotrophic receptors with oestradiol treatment may represent a coordinated response of the somatotrophic axis leading to enhanced IGF-I and -II production and improved growth rate. The inferential relationships between the capacity of the high-affinity somatotrophic receptor, plasma concentrations of IGF-I and growth rates suggest that active modulation of somatotrophic receptors is an important regulatory constituent of the somatotrophic axis.
J. Endocr . (1988) 118, 243–250
Alpha (greater than 40 microns) and gamma (less than 30 microns) motoneurons in inspiratory motor nuclei of the thoracic spinal cord of the adult cat were labelled retrogradely by the intramuscular injection of HRP. Small (less than 30 microns) unlabelled neurons within 200-300 microns of labelled motoneurons were analysed qualitatively and quantitatively with both the light and electron microscope. Most of these small unlabelled neurons had inconspicuous nucleoli, wrinkled nuclear membranes, low numbers of nuclear pores, and Nissl bodies which were either small or had the form of an amorphous perinuclear band. Such Nissl bodies were composed primarily of aggregates of polyribosomes within which short fragments of granular endoplasmic reticulum were distributed. Alpha and gamma motoneurons in contrast had prominent nucleoli, smooth-contoured nuclei, more nuclear pores and large, discrete Nissl bodies. Such Nissl bodies were composed primarily of several lamellae of granular endoplasmic reticulum with linear arrays of polyribosomes arranged between individual cisternae. Alpha motoneurons had most synaptic terminals on their cell bodies, gamma motoneurons had least and small unlabelled neurons had intermediate values. Synaptic terminals of the S-, F- T- and C-type were observed on alpha motoneurons, whereas only S- and F-types were observed on gamma motoneurons and small unlabelled neurons. Since they were unlabelled and differed morphologically from both alpha and gamma motoneurons, but were similar to small interneurons described elsewhere in the spinal cord and brain, it is suggested that the small unlabelled neurons located in the external intercostal and levator costae motor pools are interneurons. The functional significance of some of the morphological features which distinguish interneurons from motoneurons is discussed.
We have demonstrated that insulin-like growth factor I (IGF-I), at physiological concentrations, is a potent mitogen of bovine undifferentiated mammary epithelial cells cultured in collagen in serum-free medium. Its activity is independent of insulin, although at pharmacological concentrations insulin may substitute for IGF-I. The maximal [3H]thymidine incorporation stimulated by either IGF-I or insulin was only 25-40% of that in medium supplemented with 10% fetal calf serum (FCS) only. Epidermal growth factor (EGF) exhibited low mitogenic activity which was not synergistic with IGF-I in serum-free medium. IGF-I and EGF had low synergistic activity when added separately to 10% FCS-supplemented medium. Strong synergism (100% or more) was observed, however, when both factors were added simultaneously, indicating that their maximum mitogenic effect is dependent on a simultaneous presence of other factors existing in FCS. The galactopoietic effect of IGF-I was tested in organ culture of bovine lactating mammary gland. Neither fatty acid synthesis nor alpha-lactalbumin secretion was stimulated by IGF-I, even at 2000 ng/ml. These results indicate that, at least in our in vitro system, galactopoiesis is not affected by IGF-I.
The parenchymal portion of the mammary gland is immature at birth and begins to grow at a faster rate than the whole body shortly before occurrence of puberty. This accelerated or allometric growth rate is maintained for several estrous cycles, then returns to a growth rate equal to general body growth. Allometric growth of the mammary gland returns at conception and continues in most species for a variable period after parturition. Elevated secretion of estradiol and progesterone throughout pregnancy drives the allometric mammary growth during pregnancy. However, mammary growth during lactation in cows is independent of ovarian secretions and prolactin. Mammary cell numbers during lactation eventually decline as milk production decreases. Concurrent pregnancy reduces mammary cell numbers during lactation, but during the dry period concurrent pregnancy markedly increases mammary cell numbers over those in nonpregnant animals. Dry periods that are short reduce the increments in mammary cell numbers, which normally occur during early stages of the next lactation. Because numbers of mammary epithelial cells are a major determinant of milk yield, understanding the mechanisms that stimulate mammary epithelial cell numbers has the potential to lead to new methods for increasing efficiency of milk production.
A method for culturing bovine undifferentiated mammary epithelial cells embedded in collagen gels is described. Cell growth was quantitated by incorporation of tritiated thymidine. Maximal rate of incorporation was achieved in media supplemented with sera, however considerable growth was observed in serum-free medium supplemented with insulin, transferrin and selenium. The growth promoting effect of insulin was maximally expressed only at high nonphysiological concentrations.
A modified analog of human GH (hGH), prepared by recombinant DNA technology, that lacks 13 amino acids at the amino terminus (Met14hGH), was able to compete with [125I]hGH for binding to lactogenic receptors in Nb2-11C rat lymphoma cells, to somatotropic receptors in IM-9 human lymphocytes, and to both lactogenic and somatotropic receptors in the microsomal fraction of virgin female rat liver. Exposure of intact Nb2 or IM-9 cells to Met14hGH did not reduce the number of surface or intracellular receptors, as compared to the control without hormone. A parallel exposure to 500-fold lower concentrations of hGH resulted in 77-93% reduction in both surface and intracellular receptors. In contrast to [125I]hGH, [125I]Met14hGH was not taken up by the intact Nb2 lymphoma cells. Infusion of anesthetized female virgin rats for 3 h with hGH down-regulated both lactogenic and somatotropic receptors in the liver. A similar infusion with up to 200-fold higher amounts of Met14hGH did not lower the number of total receptors, indicating lack of down-regulation. Some decrease in the binding to free receptors was observed, suggesting that Met14hGH is capable of binding to liver receptors in vivo.
Nine pairs of identical twins were used to examine the effect of exogenous bovine somatotropin on mammary growth and development in dairy heifers. One twin received a daily subcutaneous injection of somatotropin (20 IU) and the other received excipient. Treatments commenced at 8.0 mo of age (179 kg live weight) and continued for 15.6 wk, at which time heifers were slaughtered and mammary development evaluated. Treatment with somatotropin resulted in an increase in mammary parenchyma and a decrease in extraparenchymal tissue and weight of mammary glands. Increases in parenchyma were 46% as determined by computer assisted x-ray tomography and 18% as determined by dissection. Differences between the two techniques related to the ability of computer assisted x-ray tomography technique to exclude fat deposits and connective tissue from parenchymal estimates. Chemical composition (39% water, 7% protein, and 54% fat) as well as histological and cytological appearance of the mammary parenchyma were not affected by the treatment. Therefore, treatment with exogenous somatotropin around puberty enhances the growth rate of mammary parenchymal tissue. Additional studies are required to examine whether this enhanced mammary development will increase milk yield during subsequent lactations.
The relationship between plasma GH profiles and circulating concentrations of insulin-like growth factor 1 (IGF-1) at three different planes of nutrition, chosen to represent a high, medium and low level of nutrition (3%, 1·8% and 1% dry matter of liveweight per day) was studied in 15 young Angus steers. All steers were maintained on 3% dry matter for 5 weeks, then on one of the three nutritional planes for 4 weeks and then all were returned to 3% dry matter for 3 weeks. Blood was sampled through jugular catheters at 15-min intervals for 25 h at the end of each phase of the study and additional samples were taken on 2 days each week.
Pulsatile release of GH occurred episodically with a diurnal increase during night and morning hours only in steers on high nutritional intakes. Reduced feeding at both the medium and the low plane abolished the diurnal rhythm and significantly increased mean plasma GH concentrations, the amplitude of GH pulses and the area under the GH profiles. Baseline concentrations of GH and pulse frequency did not change through nutritional manipulation. Upon realimentation, plasma GH concentrations decreased in both previously undernourished groups, with those fed 1% dry matter still having increased levels 10 days after refeeding. Plasma IGF-1 concentrations showed no periodicity. With nutritional deprivation, a decrease in IGF-1 concentration was observed only at negative energy balance (1% group). In this group plasma IGF-1 concentrations were progressively restored within 1 week of realimentation.
The different relationship between GH and IGF-1 release at each plane of nutrition suggests that at both medium and low levels of feed intake, tissue insensitivity to GH may exist peripherally and perhaps centrally. It is suggested that nutritional status may, through modulation of tissue sensitivity to GH, be a primary factor in determining growth and the regulation of the somatotrophic axis in the postnatal ruminant.
J. Endocr. (1986) 111, 209–215
Nucleic acid, hydroxyproline (collagen), and lipid content of mammary glands of Holstein heifers from birth to 12 months of age and on Days 0 (estrus), 2, 4, 7, 11, 18, and 20 of the estrous cycle were determined and their relationships to pituitary prolactin were studied. Deoxyribonucleic acid content of the mammary gland increased 1.6 times faster (P < 0.01) than body weight between birth and two months of age. The comparable value increased (P < 0.01) to 3.5 between five and nine months and then decreased to 1.5 from nine to twelve months of age. During the estrous cycle mammary deoxyribonucleic acid increased 118% (P < 0.05) between Day 20 and the day of estrus but declined thereafter. All other mammary constituents measured followed similar patterns of change. Thus, mammary glands of heifers were stimulated to grow at an accelerated rate well in advance of first estrus and following the initiation of estrous cycles most growth occurred during estrus. Pituitary prolactin concentration increased 333% between birth and three months and was maximum at nine months, synchronizing with similar changes in mammary development. The greatest sustained levels of prolactin in the pituitary occurred within three days before ovulation, whereas minimal levels occurred around the time of ovulation.
Somatomedin concentrations in human umbilical sera (n = 206) were measured using a specific radioimmunoassay for insulin-like growth factor (IGF)-I and a specific radioreceptor assay for IGF-II following acid-ethanol extraction of the sera to remove the somatomedin binding proteins. IGF-I concentrations were lower (P less than 0.001) than adult values and correlated with gestational age (P less than 0.001) and birth weight (P less than 0.0001). Multiple regression analysis demonstrated that both birth weight expressed independently of gestational age as the standard deviate score (P less than 0.0001) and gestational age (P less than 0.002) had effects on umbilical cord IGF-I concentrations. IGF-II concentrations were similar to adult values and did not correlate with gestational age, birth size or IGF-I values. IGF-II concentrations were higher (P less than 0.005) in male than female fetuses. These data support a role for IGF-I in influencing fetal growth and suggest the independent regulation of the secretion of IGF-I and II in the perinatal period. These was no evidence to suggest a distinct perinatal form of somatomedin.
Concentrations in blood serum of growth hormones, prolactin, insulin, and glucocorticoids were investigated in 22 pre- or postpubertal heifers fed restricted or ad libitum amounts of a ration. Gains for the respective feeding regimens were 613 and 1218 g daily. Growth hormone was elevated for prepubertal heifers on restricted feed, whereas there was no difference from feeding for postpubertal heifers. Concentrations of prolactin, insulin, and glucocorticoids were higher for heifers fed ad libitum than for those restricted. Mammary secretory tissue was positively correlated with blood serum concentrations of growth hormone, and extraparenchymal adipose tissue was negatively correlated with them. Prolactin was negatively related to mammary secretory tissue; however, this relationship disappeared after adjustment for concentrations of growth hormone, insulin, and glucocorticoids. Mammary tissue was not related to concentrations of insulin or glucocorticoids. The negative influence of excess feeding on mammary development of prepubertal heifers may be associated with a decrease in concentrations of growth hormone in blood.
No agreement exists concerning the necessity for extracting serum somatomedin (Sm) before radioreceptor assay (RRA) and RIA. We have developed a simplified system of Sm extraction which has permitted a quantitative comparison of native and extracted Sm. To 0.8 ml of a mixture of 87.5% ethanol and 12.5% 2 N HCl, 0.2 ml serum is added. After centrifugation, 0.5 ml supernatant is neutralized with 0.2 ml 0.855 M Tris base (XT). Recovery of added 125I-labeled insulin-like growth factor I ([125I]IGF-I) was nearly quantitative. Neutral gel filtration studies established that virtually all of the binding complex was removed by acid-ethanol precipitation. The addition of 100 μl Tris-neutralized acid-ethanol buffer (AE B) to the [125I]IGF-I human placental membrane RRA produced an insignificant shift in the displacement curve with patrially purified IGF reference preparation; the shift of the [125I]Sm C RIA displacement curve was greater but did not prevent accurate measurement when AE B was added to blank and standard tubes. When partially purified IGF was added to serum and extracted promptly with acid-ethanol, the added IGF was recovered completely in the extract, but when extraction was delayed until after 16 h of incubation at 4 C, there was poor recovery of added IGF, as determined by RRA. However, there appeared to be a similar recovery of endogenous Sms. The loss of added IGF was prevented by the addition of aprotinin. The RRA of XT in 9 normal sera gave results which were 2.72 ± 0.32 times higher than those obtained by direct RRA on native sera; the fold increment was 2.96 ± 0.37 when the measurements were made by Sm C RIA. Five sera from patients with hypopituitarism gave results with the RRA of XT which were only 1.12 ± 0.30 times greater than those obtained with direct assays on serum; the increment with RIA was 1.64 ± 0.23. The results of RRA on XTs in 34 sera from normal individuals, 18 patients with clinical GH deficiency, and 8 patients with acromegaly correlated well with the known GH status. We conclude that although direct serum Sm RRAs and RIAs have provided much useful information, these assays do not quantitatively measure the Sm content of serum. A simplified acid-ethanol extraction permits convenient and accurate measurement of total Sm. We suggest that direct RIA and RRA of Sm measure predominantly bound Sm. The reported lack of parallelism with equilibrium assays of native serum and the failure of quantitative recovery of Sm described here may be the result of steric and other factors which modify access of the Sm serum binding protein complex to membrane and immunobinding sites.
The replication of Nb 2 Node rat lymphoma cells in suspension culture is specifically stimulated by lactogenic hormones. Human (hPRL), ovine, bovine, and rat PRLs stimulated replication in a dose-dependent manner in the concentration range of 10 pg/ml to 1 ng/ml. Human, ovine, and bovine placental lactogens were similarly active. In addition, cell replication was stimulated by human GH (hGH), which is known to have lactogenic activity. Other hormones and growth factors examined were inactive. The growth stimulatory effects of hPRL and hGH were completely inhibited when excess anti-hPRL and anti-hGH, respectively, were added to the medium. A bioassay based on the response of the Nb 2 Node lymphoma cells to lactogenic hormones has been developed. Human serum stimulated cell replication. The effect was completely abolished if excess antibodies to both hPRL and hGH were present. The stimulation obtained with a number of human serum samples correlated very well with the sum of the hPRL and hGH concentrations in the sera, as determined by RIA (r = 0.95; P < 0.001). The concentrations of either hPRL or hGH in human serum could be individually determined by specifically blocking the growth stimulatory effect of the other hormone by adding excess anti-hGH or anti-hPRl. The sensitivity of this bioassay for PRL and hGH in serum exceeds that of RIAs.
Five studies were conducted in yearling heifers which were either puberal or prepuberal utilizing the Syncro-Mate-B (SMB) treatment (G. D. Searle & Co., Chicago, Ill.). In trial 1 the pregnancy rate in Brahman crossbred heifers after 21 days of breeding was 56% and 28% greater (P<.005) in the SMB treated groups than in the nontreated groups. Pregnancy rate in 3 4 Simmental heifers (trial 2) was increased 39% (P<.05) after 21 days of breeding. Hereford and crossbred heifers (trial 3) weighing less than 250 kg failed to respond to SMB treatment whereas heifers weighing greater then 250 kg had increased reproductive performance. Conversely the results obtained in trial 4 using Brahman crossbred heifers was not influenced by weight or SMB treatment. Crossbred Santa Gertrudis heifers (trial 5) weighing greater then 250 kg and treated with SMB had improved reproductive performance compared to the control groups. While in treated heifers weighing less than 250 kg reproductive performance was far from optimum.
The effect of prepubertal nutrition on lactation performance by dairy cows
- Johnson
Inhibition of lactogenic activities of ovine prolactin and human growth hormone (hGH) by a novel form of a modified recombinant bGH
- Ashkenazi
Control of proliferation of bovine mammary epithelial cells in vitro by hormones and growth factors
- A Shamay