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The effects of days dry and days open on the milk and butterfat production of Holstein-Friesian cattle

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The effects of days dry and days open on the milk and butterfat production of Holstein-Friesian cattle

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Abstract

The effect of days dry and days open on first, second and later lactation production was examined by intra-sire-herd-season regression. Neither variation in days dry nor days open accounted for more than 1% of the within-sire variance in fat test. Variation in preceding days dry accounted for 4.8% of the within-sire variance in milk production in second lactations but only 0.6% of the variance in later lactations. Differences in days open accounted for 4.5, 3.5, and 4.5% of the intra-sire variance in milk production in first, second, and later lactations, respectively. The effects of days dry and days open on fat production were, in all cases, slightly less than the effects on milk production. Heritabilities for both traits were low, indicating that the effects of both days dry and days open on production were largely of an environmental nature. Adjustment of milk yield for the number of days cows are open could lead to more accurate selection of dairy animals.

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... Bachman and Schairer (2003) recently published an extensive review of the literature for effects of dry period length on milk yield; therefore, this section will be a synopsis of that literature. There is an extensive list of reports that indicate reducing the DP below 50 to 60 d results in a reduction in milk yield the following lactation (Sanders, 1928;Arnold et al., 1936;Dickerson and Chapman, 1939;Klein and Woodward, 1943;Swanson, 1965;Smith et al., 1967;Wilton et al., 1967;Schaefer and Henderson, 1972;Coppock et al., 1974;Gill and Allaire, 1976;Pandy et al., 1978;Dias and Allaire, 1982;Keown and Evert, 1986;Funk et al., 1987;Sorensen and Enevoldsen, 1991; Remond et al., 1997). Many of these studies were a retrospective analysis of farm records (Sanders, 1928;Arnold et al., 1936;Dickerson and Chapman, 1939;Klein and Woodward, 1943;Wilton et al., 1967;Schaefer and Henderson, 1972;Gill and Allaire, 1976;Pandy et al., 1978;Dias and Allaire, 1982;Keown and Evert, 1986;Funk et al., 1987;Makzuka and McDaniel, 1996). ...
... There is an extensive list of reports that indicate reducing the DP below 50 to 60 d results in a reduction in milk yield the following lactation (Sanders, 1928;Arnold et al., 1936;Dickerson and Chapman, 1939;Klein and Woodward, 1943;Swanson, 1965;Smith et al., 1967;Wilton et al., 1967;Schaefer and Henderson, 1972;Coppock et al., 1974;Gill and Allaire, 1976;Pandy et al., 1978;Dias and Allaire, 1982;Keown and Evert, 1986;Funk et al., 1987;Sorensen and Enevoldsen, 1991; Remond et al., 1997). Many of these studies were a retrospective analysis of farm records (Sanders, 1928;Arnold et al., 1936;Dickerson and Chapman, 1939;Klein and Woodward, 1943;Wilton et al., 1967;Schaefer and Henderson, 1972;Gill and Allaire, 1976;Pandy et al., 1978;Dias and Allaire, 1982;Keown and Evert, 1986;Funk et al., 1987;Makzuka and McDaniel, 1996). Use of data from these studies has been criticized (Bachman and Schairer, 2003) because cows with short DP typically calved early and were not intended to have a short DP (e.g., cows with twins, cows that spontaneously aborted, cows with incorrect breeding dates). ...
... Several studies have indicated that reducing the length of the DP to less than 60 d has a more detrimental effect between the first and second lactation than between later lactations (Sanders, 1928;Wilton et al., 1967;Dias and Allaire, 1982). Increasing days dry from 0 to 50 increased milk yield the subsequent lactation by 954 kg in the second lactation and by 354 kg in later lactations (Wilton et al., 1967). ...
Article
Possible advantages of reducing length of dry period include increased income from milk production, simpli- fied dry cow management, decreased metabolic disor- ders, and alleviation of overcrowded dry cow facilities. There is abundant data to support a 60-d dry period to maximize milk yield the next lactation. The great majority of data is from studies using farm records (e.g., DHI data). In these data sets, cows with less than 6- to 8-wk dry periods probably were not intended to have short dry periods and consequently were not managed for short dry periods. Additionally, recommendations from observational data may be biased due to interac- tions, e.g., between milk yield and length of dry period. Some experiments specifically designed to compare 30- and 60-d dry periods indicate that shorter dry periods are possible without sacrificing milk production the next lactation. There is a paucity of data to determine the effects of shortening the dry period on milk composition, metabolic disorders, and reproductive performance. The limited amount of information that is available indicates that shortening the dry period will probably not have negative effects on these parameters and may have slight beneficial effects. In some cases, the beneficial effects may have resulted, in part, due to negative effects on milk production. Cows with longer calving intervals and older cows may be more likely to avoid negative effects of shortening dry periods on subsequent milk yield. Shortening the dry period by initiating milking after a dry period but prior to parturition does not in- crease milk yield or improve animal health sufficiently to warrant consideration. Several studies indicated com- plete elimination of the dry period results in a 20 to 25% decrease in milk yield the following lactation. However, these studies have utilized low cow numbers and cows with extremely low milk production. As milk yield and persistency of lactation increases, either through genetic
... LÕimpact de la rŽduction de la pŽriode s•che serait plus ŽlevŽ chez les vaches en 2 e lactation que chez les plus ‰gŽes (Sanders 1928, Wilton et al 1967, Schaeffer et Henderson 1972, dÕapr•s des Žtudes sur fichiers). En cohŽrence avec ces auteurs, Dias et Allaire (1982) estiment que la durŽe de la pŽriode s•che optimale est dÕautant plus courte que les vaches sont plus ‰gŽes. ...
... DiffŽrents auteurs ont calculŽ les corrŽlations phŽnotypiques entre la durŽe de la pŽriode s Caséines (g/kg) (Smith et Legates 1962, Wilton et al 1967, Schaeffer et Henderson 1972. Ces rŽsultats, issus de fichiers de donnŽes, pourraient sug-gŽrer que la rŽduction de la pŽriode s•che (qui va gŽnŽralement de pair avec un accroissement de la production laiti•re) Ç corrige È la diminution de fertilitŽ souvent associŽe l Õaugmentation du niveau de production. ...
... jours. D'après les résultatsde Sanders (1928),Arnold et Becker (1936),Klein et Woodward (1943),Wilton et al (1967),Coppock et al (1974),Wood (1985),Keown et Everett (1986),Sorensen et Enevoldsen (1991),Kérouanton et al (1995),Anonyme (1996). ...
Article
La politique des quotas laitiers a profondément changé le contexte économique de la production laitière, permettant aux éleveurs de se préoccuper davantage qu’auparavant de la facilité de conduite du troupeau et des risques sanitaires. Pour cela, la réduction de la durée de la période sèche, pouvant aller jusqu’à son omission, suscite un intérêt particulier. Cet article fait le point sur les conséquences de cette conduite. La réduction de la durée de la période sèche à partir de la durée standard de 6 à 8 semaines diminue la quantité de lait sécrétée au cours de la lactation suivante : d’environ 10 % pour une période sèche de 1 mois et d’un peu plus de 20 % lorsque la période sèche est omise. La forme de la courbe de lactation n’est pas modifiée. En tenant compte du lait produit en plus en fin de gestation, la réduction de quantité de lait sécrétée est inférieure à 5 % et un peu supérieure à 10 %, respectivement. La réduction de la durée de la période sèche accroît les teneurs du lait en protéines et en matières grasses pendant l’ensemble de la lactation, de sorte que la sécrétion de matière utile est moins diminuée que celle de lait. Pendant la fin de la gestation, le lait s’enrichit aussi en constituants a priori peu favorables à sa qualité (acides gras libres, immunoglobulines, plasmine et plasminogène, lipase), de façon accélérée au fur et à mesure que le vêlage approche. La forte diminution de la production laitière ne semble pas s’accompagner, du moins au cours des premières semaines de lactation, d’une réduction de la capacité d’ingestion des animaux. Leur bilan énergétique s’améliore donc fortement : les vaches perdent moins de poids en début de lactation ou n’en perdent pas du tout, et le nombre d’incidents d’origine nutritionnelle et métabolique diminue. Le raccourcissement de la période sèche, et surtout son omission, tendent à accroître le nombre de cellules somatiques dans le lait, du moins en l’absence actuelle de traitement sanitaire des mamelles adapté à cette conduite. La réduction de la durée de la période sèche pourrait permettre -cela reste à étudier- d’alimenter les vaches modernes, fortes productrices de lait, avec des régimes plus riches en fourrages qu’ils ne le sont actuellement, sans risques sanitaires accrus.
... Complete omission of the dry period results in considerable depression in milk synthesis and secretion during the next lactation. Most studies with the purpose of determining optimal dry period length have been carried out with observational data (Smith and Legates, 1962; Wilton et al., 1967; Smith and Becker, 1995). Recently, several designed studies have evaluated dry period lengths. ...
... We speculate that short dry periods do not provide sufficient time for cell turnover, especially in primiparous cows. Our findings agree with those of others (Wilton et al., 1967; Gulay et al., 2003; Annen et al., 2004). Discrepancies in results of different studies on interaction of dry period length and parity apparently arise from management schemes (Gulay et al., 2005; Rastani et al., 2005), genetic potential of milk yield (), experimental method (between-cow model or within-cow and half-udder model) and statistical power. ...
Article
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To evaluate effects of different dry period lengths on milk yield, milk composition, and energy balance of dairy cows, 122 multiparous and primiparous Holstein dairy cows were used in a completely randomized experimental design with 56-, 42-, and 35-d dry period lengths. Actual dry period lengths for respective treatments (TRT) were 56 +/- 5.1 d, 42 +/- 2.1 d, and 35 +/- 2.7 d. Overall, cows in the 42- and 56-d TRT gained more body condition than those in 35-d TRT during the dry period; however, postpartum body condition score did not change substantially among the TRT. Although from 3 to 210 DIM, differences were not detected in the milk yield of multiparous cows between the 35- and 56-d TRT, primiparous cows in the 35-d TRT produced less milk than those in 56-d TRT. In primiparous cows, the milk production at wk 9, 10, and 11 of lactation was lower in the 35-d compared with the 56-d TRT. Primiparous cows in the 35-d compared with the 56-d TRT produced less milk protein. In the 35-d TRT, serum triglyceride concentration was greater in primiparous cows than in multiparous cows during the peripartum period. Among primiparous cows, those in the 56-d TRT had greater concentrations of nonesterified fatty acids than those in the 35-d TRT during the peripartum period. No significant differences were observed in concentrations of serum glucose, insulin, and insulin-like growth factor-I during early lactation among TRT. There was also no difference among TRT for incidence of metabolic disorders. Thus, this study indicates that shortening the dry period to 35 d may be beneficial in multiparous and overconditioned cows, but not in primiparous cows.
... Since the level of production has varied so much across experiments, the effect of dry period length on the subsequent lactation was expressed as a proportion of production obtained at 56 to 65 days (60-d dry period). Figure 1 summarizes data from planned (Annen et al., 2003; Annen et al., 2004; Bachman, 2002; Coppock et al., 1974; Gulay et al., 2003; Rastani et al., 2003; Remond et al., 1997; Sorenson and Enevoldsen, 1991; Swanson, 1965) and retrospective studies (Dias and Allaire, 1982; Funk et al., 1987; Keown and Everett, 1986; Klein and Woodward, 1943; Makuza and McDaniel, 1996; Schaeffer and Henderson, 1972; Wilton et al., 1967). ...
... Prior to abandoning previous recommendations based on retrospective analyses of DHIA data, I believe that comparisons of productive losses predicted by retrospective analyses and those found in experiments where dry period length was intentionally altered (planned) should be made. Since the level of production has varied so much across experiments, the effect of dry period length on the subsequent lactation was expressed as a proportion of production obtained at 56 to 65 days (60-d dry period).Figure 1 summarizes data from planned (Annen et al., 2003; Annen et al., 2004; Bachman, 2002; Coppock et al., 1974; Gulay et al., 2003; Rastani et al., 2003; Remond et al., 1997; Sorenson and Enevoldsen, 1991; Swanson, 1965) and retrospective studies (Dias and Allaire, 1982; Funk et al., 1987; Keown and Everett, 1986; Klein and Woodward, 1943; Makuza and McDaniel, 1996; Schaeffer and Henderson, 1972; Wilton et al., 1967). ...
... Illustration of the effects of genetic gain and management practices on peak milk yield and lactation persistency (Adapted from Knight, 1998). period is optimal (Klein and Woodward, 1943; Wilton et al., 1967; Schaeffer and Henderson, 1972; Coppock et al., 1974; Funk et al., 1987; Sørensen and Enevoldsen, 1991). The majority of these conclusions are derived from surveys of dairy records (from herds managing for a 60-d dry period) rather than controlled studies. ...
... They concluded that continued body and mammary growth in primiparous cows resulted in larger production losses after a shortened or omitted dry period. Further, several studies analyzing dairy records also detected a greater sensitivity of a reduced or omitted dry period between the first and second lactations than in older cows (Wilton et al., 1967; Dias and Allaire, 1982). Dias and Allaire (1982) determined that as age at calving in the lactation before a shortened dry period increased from 24 to 83 mo, the optimal number of dry days decreased from 65 to 23 d. ...
Article
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A dry period, typically 40 to 60 d, between lactations is believed to be required to maximize milk yield in the subsequent lactation. Several hypotheses have been proposed to explain the requirement for the dry period, including (1) replenishment of body reserves, (2) regen-eration of mammary tissue, and (3) optimization of ben-efits from endocrine events near the time of parturition. Continuously milked cows or glands have depressed milk yields but no differences in mammary DNA con-tent or cell number. Nutritional status and endocrine hormones are not factors in reduced milk yield in con-tinuously milked glands. Data from continuous lacta-tion studies suggest that depressed milk yields are due to reduced functionality of mammary parenchyma. There is a need to reevaluate effects of continuous lacta-tion on milk yield in today's high-producing dairy cow because studies on this topic were done using cows achieving peak milk production of 18 to 30 kg/d com-pared with 45 to 50 kg/d in today's dairy cows. Another factor that has not been considered in conjunction with current milk production levels is the use of bovine soma-totropin (bST). Supplementation with bST increases milk yield, improves lactation persistency, and may im-prove milk yield in continuously milked cows. Future research goals are to examine the effects of continuous lactation in high-producing cows and to determine the effects of bST on milk yield and mammary functionality in continuously milked cows. (Key words: dry period length, management, mam-mary development, bovine somatotropin) Abbreviation key: CM = continuous milking; MEC = mammary epithelial cells, TGF-β1 = transforming growth factor β1.
... Similar postpartum milk production between cows on the treatment 1 and 2 is consistent with the finding of [29]- [3]- [22] and [15]. But references [31]- [24] and [34] suggested that managing cows for dry periods of approximately 30 to 35 days resulted in decreased milk yield during the subsequent lactation compared to cows given 60-day dry periods. ...
... Our data about postpartum serum NEFA concentrations are in opposite with [34] that reported postpartum NEFA concentrations were lower for cows assigned to shortened 34-d dry period compared with 55-d DP. ...
Article
Twenty -nine Holstein cows were used to evaluate the effects of different dry period (DP) lengths on milk yield and composition, some blood metabolites, and complete blood count (CBC). Cows were assigned to one of 2 treatments: 1) 60-d dry period, 2) 35-d DP. Milk yield, from calving to 60 days, was not different for cows on the treatments (p =0.130). Cows in the 35-d DP produced more milk protein and SNF compare with cows in treatment 1 (p ≤ 0.05). Serum glucose, non-esterified fatty acids (NEFA), beta hydroxyl butyrate acid (BHBA), blood urea nitrogen (BUN), urea, and glutamic oxaloacetic transaminase (GOT) were all similar among the treatments. Body condition score (BCS), body weight (BW), complete blood count (CBC) and health problems were similar between the treatments. The results of this study demonstrated we can reduce the dry period length to 35 days with no problems.
... A majority of the literature indicates that to achieve maximal milk production, a nonlactating or dry period (DP) is necessary between lactations. However, this literature is mostly retrospective analysis of farm records (Sanders, 1928;Arnold and Becker, 1936;Klein and Woodward, 1943;Wilton et al., 1967;Schaeffer and Henderson, 1972;Gill and Allaire, 1976;Pandey et al., 1978;Bar-Anan and Soller, 1979;Oltenacu et al., 1980;Dias and Allaire, 1982;Keown and Everett, 1986;Funk et al., 1987;Makuza and McDaniel, 1996). Cows in these studies with less than a 6-to 8-wk DP probably were not intended to have short DP and probably were not managed for a short DP (e.g., cows carrying twins, cows with late-term abortions, cows with incorrect breeding/calving date, cows only fed the far-off diet). ...
Article
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Sixty-five Holstein cows were used to evaluate management schemes involving altered dry period (DP) lengths on subsequent milk production, energy balance (EB), and metabolic variables. Cows were assigned to one of 3 treatments: traditional 56-d DP (fed a low-energy diet from -56 to -29 d and a moderate energy diet from -28 d to parturition; T), 28-d DP (continuously fed a high energy diet; S), and no planned DP (continuously fed a high energy diet; N). Prepartum DM intake (DMI), measured from 56 d prepartum through parturition, was lower for cows on the T treatment than for cows on the S treatment and was higher for cows on the N treatment than for cows on the S treatment. There were no differences in prepartum plasma glucose, and beta-hydroxybutryric acid; there was a treatment by time interaction for prepartum plasma nonesterified fatty acid (NEFA). There was no difference in prepartum liver triglyceride (TG); postpartum liver TG was decreased for cows on the N treatment compared with cows on the S treatment, but was similar for cows on the T and S treatments. Postpartum NEFA was similar between cows on the T and S treatments, but was greater for cows on the S treatment than for cows on the N treatment. Postpartum glucose was greater for cows on the N treatment compared with cows on the S treatment and tended to be greater for cows on the S treatment than for cows on the T treatment. There was no difference in postpartum solids-corrected milk (SCM) production or DMI by cows on the T vs. S treatment. However, there was a tendency toward lower postpartum SCM production by cows on the N vs. S treatment and a tendency for greater postpartum DMI by cows on the N vs. S treatment. Postpartum EB was greater for cows on the S vs. T treatment and the N vs. S treatment. In general, T and S management schemes had similar effects on DMI, SCM, and metabolic variables in the first 70 d of the subsequent lactation. Eliminating the DP improved energy and metabolic status.
... A decreased production response has also been reported for rbST-supplemented primiparous cows provided an SDP of 30 days (Annen et al., 2004b). This parity sensitivity to CM or SDP was observed previously in commercial trials (Remond et al., 1997a and1997b) and in retrospective studies of dairy records (Wilton et al., 1967;Dias and Allaire, 1982). As might be expected, the impact of SDP on milk yield loss is not as great as CM. ...
Article
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The dry period is required to facilitate cell turnover in the bovine mammary gland in order to optimize milk yield in the next lactation. Traditionally, an 8-week dry period has been a standard management practice for dairy cows based on retrospective analyses of milk yields following various dry period lengths. However, as milk production per cow has increased, transitioning cows from the nonlactating state to peak milk yield has grown more problematic. This has prompted new studies on dry period requirements for dairy cows. These studies indicate a clear parity effect on dry period requirement. First parity animals require a 60-day dry period, whereas lactations following later parities demonstrate no negative impact with 30-day dry period or even eliminating the dry period when somatotropin (ST) is also used to maintain milk yields. Shortened dry periods in first parity animals were associated with reduced mammary cell turnover during the dry period and early lactation and increased numbers of senescent cells and reduced functionality of lactating alveolar mammary cells postpartum. Use of ST and increased milking frequency postpartum reduced the impact of shortened dry periods. The majority of new intramammary infections occur during the dry period and persist into the following lactation. There is therefore the possibility of altering mastitis incidence by modifying or eliminating the dry period in older parity animals. As the composition of mammary secretions including immunoglobulins may be reduced when the dry period is reduced or eliminated, there is the possibility that the immune status of cows during the peripartum period is influenced by the length of the dry period.
... Dry period of length 60 days is must to maintain the milk production in subsequent lactation. Sørensen&Enevoldsen, Wilton, Madsen and Rastani [17][18][19][20] also suggested that dry periods of around 30 to 35 days resulted in decreased milk yield in the next lactation compared to cows with dry period of 60 days. ...
Research
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One hundred and fifty four water buffaloes of Chitwan district were used to determine the variations in the composition of raw milk and milk yield due to pregnancy and dry period. Primary data for the study was collected using a well-designed questionnaire. Effect of dry period length and pregnancy were taken under consideration that determines the lactational efficiency. Effect of pregnancy on various milk components was also studied. The components analyzed in milk were fat, protein, SNF, density, lactose, total solid and salt. For better understanding the effect of pregnancy, the data obtained were categorized into two classes: pregnant and non-pregnant. The data thus obtained was analyzed using SPSS version 24. Fresh milk samples were collected and analyzed using milk analyzer in the laboratory. Results of present study unveiled that the salt, protein, lactose and SNF content in milk of non-pregnant buffalo is significantly lower (p<0.01) than that of pregnant one. But fat, density and total solid content of milk of pregnant buffalo had no significant difference (p>0.05) than that of non-pregnant one. Results also revealed that the length of dry period has significant effect on milk components and total yield. Among all other milk components, salt content in milk shows higher level of significance (p<0.05). The significant effect (p<0.05) of pregnancy on milk yield is generally observed after the 5th month of gestation.
... There was no treatment by time or treatment by parity interaction for milk production. The lower level of milk production by cows on S as compared to C along with the lower production of cows in their second versus third lactation has been reconfirmed by this trial Annen et al., 2004;Wilton et al., 1967). Milk fat percentage was not affected by treatment with C producing 3.42% and S producing 3.52% milk fat (P < 0.10) ( Table 1). ...
... Research is inconsistent regarding parity by dry period length interaction. Several studies have indicated that reducing the length of the dry period to less than 60 days has a more detrimental effect between the first and second lactation than between later lactations (Sanders, 1928;Wilton et al., 1967;Dias and Allaire, 1982;Annen, 2004). However, other analyses have indicated no interaction between parity and optimal length for the dry period (Keown and Everett, 1986;Funk et al., 1987;Sorensen and Enevoldsen, 1991;Rastani et al., 2005). ...
... In a second experiment, they also reported that shortening the dry period from 55 to 34 days resulted in fewer days to first ovulation, fewer days open, and a higher percentage of cows pregnant at 150 days in lactation; although the improvement in the last two reproductive parameters was only significant for cows with 3 or more lactations. Despite the current growing interest in reassessing the duration of the dry period, arguing that a shorter dry period could have advantages over a conventional dry period from 55 to 70 days, as an alternative to improve the reproductive performance shorting the open period (Grummer et al. (2010;Pezeshki et al. 2007;Rastani et al. 2005 ), to get higher income from milk production, simplified management of dry cows, reduction of metabolic disorders and relief of overcrowded dry cow facilities (Grummer and Rastani, 2004), a dry period of around 60 days is still routinely recommended since dry periods of less than 40 days have resulted in a substantial reduction in milk production in the next lactation (Klein and Woodward, 1943;Wilton et al., 1967;Schaeffer and Henderson, 1972;Coppock et al., 1974;Funk et al., 1987;Sørensen and Enevoldsen, 1991). The decision to implement a shorter dry period would depend on the results of many more studies and consideration of other economically important parameters such as cow health and longevity. ...
Chapter
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This article is part of the "Dairy Production Teaching Notes" series, an informational material developed for undergraduate students of animal science and veterinary medicine. These articles present basic information and in a simple way about the main practices used in the management and breeding of dairy cattle.
... A dry period has been established as a necessary management practice to maintain profitable milk production in dairy cows (Bachman and Schairer, 2003). In past decades, a dry period of 60 days has been routinely recommended as optimal, and a dry period fewer of 40 days has resulted in reduced milk yields in the succeeding lactation (Klein and Woodward, 1943;Wilton et al., 1967;Schaeffer and Henderson, 1972;Coppock et al., 1974;Funk et al., 1987;Sørensen and Enevoldsen, 1991). Numerous studies support that 60 days dry period, permit to maximize milk yield the next lactation; though in most of studies were used farm records (e.g., DHI data). ...
... For example, an early study (Klein and Woodward, 1943) using DHI records from consecutive years showed that milk yield was lower when the dry period was below 30 d than when it was more than 30 d. In another study (Wilton et al., 1967), the Canadian record system showed slightly lower milk yields when cows were dry for 30 d than for 60 d. Recommendations from these types of studies were based on retrospective data analyses. ...
... Complementing the cellular level research that suggests omitting a dry period is not advantageous in terms of milk production in cows, another large body of literature has focused on understanding the ideal dry period length. Early retrospective reviews of milk production records suggested that dry periods of 30 d or less had negative effects on milk production in subsequent lactations of dairy cows (e.g., Klein and Woodward, 1942;Wilton et al., 1967). However, with the potential financial gains of shorter dry periods (e.g., Santschi et al., 2011b) being considered, research in this area has continued, collectively demonstrating the complexity of choosing the correct dry period length. ...
Article
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The forced cessation of milk production, or dry-off, is a routine management practice in dairy cattle, sheep, and goats. This practice initiates a dry period, during which the animal is not milked. Milking begins again after parturition. Most of the literature on the dry period has focused on how various drying-off strategies affect milk production and disease; little work to date has addressed how dry-off affects the overall welfare of the dairy animal. The first aim of this review was to present an overview of the importance of dry-off and how it is commonly achieved. Our review shows that much scientific progress has been made in improving health status between lactations. The second aim was to identify important gaps in the literature, of which 2 key research disparities have been identified. We find that much of the work to date has focused on cattle and very little research has examined dry-off in dairy sheep and goats. We also find a lack of research addressing how common dry-off methodologies affect animal welfare on more than just a biological level, regardless of species.
... Days open length was found to have significant influence on 305-day milk yield by several investigators (e.g. Wilton et al , 1967 ;Basu et al , 1979Basu and Ghai , 1980 ;Juma and Jajo , 1986 ;Mohamed , 1987 ;Khattab and Ashmawy , 1988 ;Abdel-Glil , 1991 ;Salem , 1991 ;Khalil et al , 1994) . Also , Gad (1995) revealed that days open length is one of the most important factors affecting 305-day milk yield . ...
Thesis
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Data of milk production traits (305-day milk yield ; length of lactation period ; dry period ) and reproductive ones (calving interval ; age at first calving ) using 5662 normal lactations produced by 1029 Holstein cows during nine consecutive years started by 1984 in a commercial herd of Holstein cattle located in El-Salhia farm , Ismailia Governorate , Egypt , were used in this study . The objectives of this study were : (1) to test the significance of sire and non-genetic fixed factors influencing milk production and reproductive traits of the study by using the least-squares Maximum Likelihood mean weighted program (Harvey , 1990) , (2) to obtain the components of variance for each trait and covariance between each pair of these traits through the Restricted Maximum Likelihood (REML) procedure (SAS , 1996) to be used as starting values needed for applying the multi-trait animal model analysis and (3) to obtain heritability estimates for each of milk production and reproductive traits of the study in addition the coefficients of genetic and phenotypic correlation coefficient among all traits of the study once when using data of all available lactations produced and another time when using only data of the first lactation . (4) to estimate breeding values of cows , sires , and dams once whenusing data of all available lactations and another time when using only data of the first lactation . Actual means of the studied traits , genetic parameters and breeding values were obtained through analyzing the data by Multiple trait Derivative Free Restricted Maximum Likelihood (MTDFREML) procedure (Meyer , 1998) using multi-trait Animal model Analysis . The main results obtained can be summarized as follows: 1- Sire constituted a significant source of variation in 305-day milk yield , length of lactation period dry , period , and calving when interval when analyzing data of all available lactations . Also, sire effect was found to be significant on dry period, calving interval and age at first calving when analyzing data of only the first lactation 2- When using data of all available lactations, year of calving, season of calving, age at calving, days open effects were proved to be significant on 305-day milk yield, length of lactation period and dry period. Also, year of calving, season of calving and age at calving showed significant effects on calving interval. 3- When using only records of the first lactation, year of calving and age at calving showed significant effects on 305-day milk yield and calving interval length. Season of calving had significant effect on only dry period. Days open effect was found to be significant on 305-day milk yield, length of lactation period and dry period, season of birth and the interaction between year of birth and season of birth influenced age at first calving significantly. 4- Heritability estimates calculated when using data of all the available lactations were 0.24, 0.07, 0.05 and 0.07 for 305-day milk yield, length of lactation period, dry period and calving interval, respectively. 5- Heritability estimates obtained when using data of only the first lactation were 0.43, 0.31, 0.09, 0.05 and 0.04 for 305-day milk yield, length of lactation period, dry period, calving interval and age at first calving, respectively. 6- The genetic correlation coefficients, reached by analyzing data of all the available lactations, among milk production traits of the study and calving interval were positive except those between dry period and each of 305-day milk yield and length of lactation period were negative. Their magnitudes ranged from low to high. At the same time 50% of the phenotypic correlation coefficients among the same traits, when using data of all available lactations, were positive the remainder 50%were negative and also their magnitudes ranged from low to high. 7- Most of the genetic correlation coefficients, obtained by analyzing data of only the first lactation, were positive and the remainder ones were negative. The same picture was shown with the phenotypic correlation coefficients. 8- Breeding values of cows , sires and dams for milk production and reproductive traits the study were obtained once when using data of all available lactations and another time when using only data of the lactation . 9- The ranges of cow breeding values for all traits of the study were always higher their then corresponding's of either sire or dam breeding values. Therefore, it could be concluded that selecting cows for milk production and reproductive traits of the study according to the cow breeding values would be more reasonable and efficient than selecting them according to their sire's or dam's breeding values.
Article
In three studies of 51,618 Holstein, 6,630 Jersey, and 1,524 Guernsey records, correlation was .07 between 120-day milk yield and number of services required for probable conception, independent of days postpartum. The partial regression coefficient for Holsteins was .014 +/- .001 more services for each additional 100 kg of 120-day milk. For Jerseys and Guernseys, .028 +/- .008 more services were required for each additional 100 kg of 120-day milk.
Article
Objectives were to determine effects of continuous milking (CM) and bovine somatotropin (bST) administration on 1) mammary epithelial cell (MEC) proliferation, apoptosis, and ultrastructure during late gestation and early lactation, 2) expression of genes associated with proliferation, and apoptosis in mammary epithelial cells, and 3) milk yield and composition. Second-gestation, first dry-period cows were randomly assigned to either continuous bST throughout late gestation and early lactation (+bST; n = 4) or no bST (-bST; n = 4) administration. Within each animal, udder halves were randomly assigned to CM or a 60-d dry period (control) treatment. Daily milk yield and weekly milk composition were measured during the last 60 d of gestation in CM halves and from 1 to 30 d postpartum for both halves. Mammary biopsies were obtained at -20 +/- 7, -8 +/- 3, +1 +/- 0, +7 +/- 0, and +20 +/- 0 d (mean +/- standard error) relative to parturition. Prepartum half-udder milk yield was greater in +bST cows than in -bST cows (9.9 vs. 8.2 kg/d) and postpartum half-udder milk yields were dramatically reduced in CM halves compared with control halves (10.6 vs. 22.2 kg/d), regardless of bST treatment. Proliferation of MEC was reduced in CM halves at -8 d (2.7 vs. 5.4%). Apoptosis of MEC was elevated during early lactation for d +1 and +7 in control halves, but was only increased at d +1 in CM halves. Turnover of MEC was not affected by bST. Ultrastructure data indicated complete involution of the control half and lactation maintenance in CM glands (d -20). By d -8, control tissue contained alveoli in an immature secretory state, but CM tissue contained both lactating and immature alveoli. Postpartum ultrastructure parameters were similar between halves until d 20 when control tissue was composed of a homogeneous population of lactating alveoli, but CM tissue contained lactating, engorged, and resting alveoli. Expression of CCAAT/enhancer binding protein-beta (CEBP-beta), cyclin D1, and bcl(2) were up-regulated during late gestation, but did not differ between control and CM halves. Expression of alpha-lactalbumin was increased in CM halves during late gestation, but was not different in CM and control tissue after parturition. Other genes evaluated (bax, insulin-like growth factor binding protein 5, ATP-binding cassette 1, and p27) were not differentially expressed at any timepoints evaluated. Results indicate that CM reduced subsequent half-udder milk yield in primiparous cows through altered MEC turnover and secretory capacity. Negative effects of CM on the subsequent lactation were not alleviated by bST supplementation.
Article
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Peak milk yield, lactational persistency and conception rates were studied using 5928 lactation records of high milk-producing cows at three California dairies. Log-linear analysis was used to study relationships between peak milk yield, lactational persistency, dairy of origin, lactation number and conception rates in 3850 completed lactations. Cows with peak milk yields greater than the median (38.2 kg milk per day) were less likely to have conceived in one or two breedings than cows with peak milk yields lower than or equal to the median. Cows with a higher than median (0.755) lactational persistency were less likely to have conceived in one or two breedings than cows with a lactational persistency lower than or equal to the median. Dairy of origin had a significant effect on the probability of conceiving in one or two breedings. Cows in the first lactation were more likely than those in subsequent lactations to conceive in one or two breedings. This retrospective study demonstrated that subfertility is associated with high peak lactational yields in high milk-producing California cows.
Article
Dry periods of 40 to 60 d have been an industry standard because dry periods <40 d have resulted in reduced milk yields in the subsequent lactation by 10 to 30%. However, recent research has demonstrated no production losses for cows given a 30-d dry period. The current study evaluated milk production effects of shortened or omitted dry periods for cows at mature-equivalent production >12,000 kg of milk and treated with bovine somatotropin (bST). The study used 2 commercial dairies and one university dairy and included 4 treatments. Five multiparous and 5 primiparous cows from each farm were assigned to each treatment: 1) 60-d dry period, label use of bST (60DD); 2) 30-d dry period, label use of bST (30DD); 3) continuous milking, label use of bST (CMLST); and 4) continuous milking with continuous use of bST (CMCST). Per label, bST use started at 57 to 70 d in milk and ended 14 d before drying (60DD and 30DD) or expected calving date (CMLST). In primiparous cows, average milk yields during the first 17 wk of lactation were reduced for cows on treatments 30DD, CMLST, and CMCST vs. the 60DD treatment. (38.3, 35.1, and 37.5 vs. 44.1 ± 1.3 kg/d, respectively). For multiparous cows, respective milk yields did not differ (46.6, 43.4, 46.5, and 47.7 ± 2.1 kg/d). Shortened or omitted dry periods may impede mammary growth in primiparous cows, resulting in reduced milk yield in the subsequent lactation. In contrast, a shortened or omitted dry period with either bST protocol did not alter production in multiparous cows treated with bST. Quality aspects of prepartum milk and colostrum require additional characterization. For multiparous cows, milk income generated for short dry periods or for continuous milking might increase their profitability. At 17 wk of the subsequent lactation, estimates of the cumulative net margins of multiparous cows on the 30DD treatment and continuous milking treatments exceeded those of cows on the 60DD treatment by $40 to $60 per cow.
Article
Milk production per cow has increased as a result of progressive changes in the genetics and management of the dairy animal population. A management constant during many decades of progress has been the widely adopted dry period length of 51 to 60 d. The scientific basis for that industry standard was examined to assess its validity as the appropriate standard for the modern dairy industry. If subsequent milk yields can be sustained fully after dry periods that are shorter than the current standard, then considerable milk is being forfeited by retaining longer dry periods. Conversely, failure to allow any dry period will result in a significant decrease in subsequent milk synthesis and secretion. Most studies to determine the minimum length of dry period required have involved retrospective analyses of observational data. Only five experiments have been reported in which dairy cows were assigned, at random, to planned 30- and 60-d dry periods. Estimates of the change in subsequent milk production when days dry were decreased from 50 to 57 d to 30 to 34 d ranged from a 10% decrease to a 1% increase. However, lower yields after shorter dry periods may be partially offset by greater milk yields in the previous lactation if such cows are milked 3 to 4 wk longer. Environmental factors that influence milk production as well as the biological processes that occur within the mammary gland during the nonlactating period must be considered when dry period lengths are compared. Importantly, additional animal trials that specifically assign cows randomly to the dry period lengths to be evaluated are needed to determine optimal dry period lengths for modern dairy cows in differing management scenarios.
Article
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To identify risk factors for culling of dairy cows from eight New South Wales dairy herds. A longitudinal population study of dairy cow culling in eight non-seasonally calving dairy herds in the Camden district of New South Wales. Cox's proportional hazards model was used to evaluate various risk factors for culling for a specific reason (sales, deaths, reproductive failure, disorders of the udder and low milk production). Age at first calving was not a significant risk factor for culling. Milk production in the first lactation greater than the population mean did not influence length of productive life overall, but was associated with a greater hazard of removal for disorders of the udder. Risk of culling for reproductive failure differed significantly between farms, and was not related to events in the previous lactation such as calving-to-first service interval or calving-to-conception interval. Shorter calving intervals were associated with increased risk of removal for low milk production and disorders of the udder. Longitudinal surveys to accurately identify reasons for removal from a wide range of herds, identification of herds with low culling rates (especially for reproductive failure and udder disorders), and the identification of practices associated with these culling rates would be worthwhile to the Australian dairy industry.
Article
Effects of days dry and previous and current days open on milk yields during the first three lactations were determined for Holsteins from Zimbabwe and North Carolina. The animal models used included animal; permanent environmental effects of cows for herd-year, month of calving, age, current days open, and DIM; and the inverse of additive numerator genetic relationships. Model 1 for first lactations included only these effects, but Model 2, the animal model for later lactations, included these effects plus previous days open, previous days dry, and previous milk yield. The dependent variable in both models was unadjusted milk yield for the lactation. Current and previous days open, previous days dry, and DIM were also fitted as dependent variables with Models 1 and 2, except for previous milk yield, when appropriate. As current days open increased, milk yield rose, regardless of milk yield during prior lactations. Milk yields were reduced for lactations following < 60 d dry and showed little advantage for longer dry periods. The effects of previous days open are real but are overestimated unless permanent environmental effects of cows are considered simultaneously. The heritabilities and repeatabilities of current and previous days open and previous days dry were higher for cows in Zimbabwe than for those in North Carolina. Results suggest that, to obtain unbiased estimates of breeding values of sires and cows, yield data should be adjusted for the environmental effects of days dry as well as those of previous and current days open.
Article
Dairy Herd Improvement testing records of 201 dairy herds of sizes from under 100 to over 1000 cows and herd average milk yields from under 5,000 to over 10,000 kg were studied. Average days to first postpartum breeding tended to be less in herds of over 500 cows. Herds of 300 to 600 cows had highest production per cow. Herds with higher average yields averaged shorter intervals to first postpartum breeding and fewer days open. Days open included farrow cows arbitrarily assigned 305 days open. Number of breedings changed little as herd yield increased, but days open for highest producing herds averaged one estrous period shorter than for low producing herds, suggesting better detection of estrus. For the individual cow, high yield or associated factors have a small but real antagonistic association with reproductive efficiency. Days to first breeding, to last breeding, and days open increased .27, .80, and .61, and number of breedings increased .014 for each 100 kg increase in 180-day yield of fat-corrected milk. The record averages of high-producing herds indicate this antagonism may be overshawdowed by good management; effective estrus detection probably is a major factor.
Article
Breeding receipts from artificial insemination were matched with records of milk yield from northeastern United States. Nine measures of yield and 10 measures of fertility were investigated. A completely random model with herd-year-season, sire, and interaction of sire by herd-year-season was applied by parity; interaction of sire by herd-year-season was not important except possibly for fertility of virgin heifers. Sires accounted for 6 to 7% of yield variation and herd-year-seasons accounted for about 45%. Measures of fertility had small sire variances, and herd-year-season variance was much smaller than for yield. Effects of age within parity were significant for yield from ordinary least-squares analysis. Age adjustment factors were obtained for measures of yield. Repeatabilities of first- and second-parity yield ranged from .40 to .61 whereas repeatabilities of fertility were .03 to .13. Repeatabilities of virgin heifer and first-parity fertility were .01 to .03, suggesting heifer and cow fertility may not be related.
Article
Influences of days open present lactation, days open previous lactation, and days dry previous lactation were fit simultaneously to determine their effects on measures of yield, which were fat-corrected milk, milk, and milk fat, all adjusted to a 305-d mature equivalent basis. Best linear unbiased estimates were obtained. Multiparity analyses were conducted using a model in which later parity records could be compared with more unselected first parity records. Additional parity information made little difference in the influence of previous days dry and previous and present days open on yield. As present days open increased from 20 to 300 d, lactation yields for FCM, milk, and milk fat increased approximately 1250, 1350, and 45 kg. As previous days open increased from 20 to 300 d, lactation yields for FCM, milk, and milk fat increased approximately 625, 650, and 25 kg. Cows dry 60 to 69 d gave the most milk the following lactation. Cows dry less than 40 d produced much less milk the next lactation. Heritability estimates for previous days dry were less than 7%. Multiplicative adjustment factors were developed to adjust lactation yield records for the largely environmental effects of days open and days dry.
Article
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The effect of planned dry period lengths of 4, 7, and 10 wk on subsequent lactational yield was estimated with 366 cows in an experiment in which dry period was manipulated independently of milk yield prior to drying off. In two herds, all three treatments were compared within herd; in six herds, two treatments were compared within herd. Compared with a 7-wk planned dry period, a 3-wk decrease lowered the level of milk production by 2.8 kg of 4% FCM/d in the first 84 d of the subsequent lactation, whereas a 3-wk increase raised the level of milk production by .5 kg/d. In the first 168 d of the subsequent lactation, the difference between 4-wk and 7-wk planned dry periods was 2.7 kg/d, and the difference between 7- and 10-wk periods was .4 kg/d. There was no indication of interaction among planned dry period length and lactation number, days open in previous lactation, previous milk yield, breed, or health status with respect to effect on subsequent lactational yield.
Article
Holstein lactation records from the Dairy Herd Improvement test day files of the New York Dairy Records Processing Lab- oratory at Cornell University were used to study genetic and environmental relation- ships of days dry and days open with milk production. Age and month of calving significantly influenced length of dry period. Within herd heritability estimates of days dry were .15, .33, and .34 for second, third, and later lactations. Within herd heritability estimates of days open were essentially zero. As the length of open period increased, cumulative milk production also increased at each successive stage of lactation. Differences of days open groups for 305-day milk yield were used to prepare adjustment factors for days open.
Article
Holstein sires were evaluated by the Northeast Artificial Insemination Sire Comparison method from 227,232 mature equivalent 305-day ~rst lactation milk records. Records were adjusted for period open, and sires were reevaluated by the same procedure. Evaluations changed even for sires having more than 2,000 daughters. The average change in evalu- ations was nearly zero, and the correla- tion of deviations between the two com- parisons with the original evaluation was zero. Thus, changes in evaluation were independent of a sire's genetic value. A separate study indicated that Hol- stein adjustment factors can serve for all breeds on a praclJcal basis. Heritabili- ties of days open were essentially zero for each breed.
Article
A model of the drying off decision problem was constructed in which the effect of parity, month of freshening, length of dry period prior to lactation, and the length of open period during the current lactation on milk production were considered. The seasonal variations in the price of milk and feed costs were also considered. The net return per year was used to compare the effect of different times of drying off. Optimum length of dry period for first lactation cows freshening in summer to fall was 47 to 49 d if open between 40 and 160 d and 50 to 53 d if open more than 160 d. For cows freshened during winter to spring, the optimum dry period was 50 to 53 d if open between 40 and 130 d and 53 to 63 d if open more than 130 d. For mature cows freshening during summer to fall, the optimum dry period was 48 to 56 d if open between 40 and 130 d and 56 to 84 d if open more than 130 d. If cows freshened during winter to spring, the optimum length of dry period was 51 to 54 d, 54 to 85 d, and 80 to 112 d for cows open 40 to 70 d, 70 to 130 d, and more than 130 d, respectively.
Article
The effects of common clinical and two subclinical disease conditions (mastitis and ketosis) on milk production and reproductive performance in Holstein-Friesian cows were investigated in a two and a half year study. The data used were from 1315 lactation records and results from tests performed on 6241 composite milk samples.Path analyses were used to estimate the direct and indirect impact of disease on days to conception, milk production in a standard 305 day lactation and milk production per day. Indirect effects accounted for a large percentage of the total effect of some diseases on production. The path coefficients were quite sensitive to the units used to measure production, with deviation from the herd average being the preferable measure. These units controlled confounding due to herd level variables. Effects identified by the path analyses were substantially different from those determined on the basis of unconditional associations between diseases and production parameters.Subclinical mastitis and the reproductive diseases (most of which were subclinical in nature) were found to have the greatest detrimental impact on milk production per day. Several disease conditions had a beneficial effect on milk production and this was attributed to the therapy provided to cows affected with these conditions. All conditions related to reproductive performance had a detrimental effect on days to conception.
Article
A total of 2352 complete lactation records of Friesian cows, raised at Dalla farm which is 130 km from Cairo, Egypt, during the period from 1987 to 1992, were used to determine the effects of days open and days dry on milk and fat yields. A least squares analysis of variance was done for each trait using a model which included season and year of calving, parity, days open and days dry with possible interactions between year by season, year by parity and season by parity. The least squares analysis of variance showed the significant effects of all factors and probable interactions on 305-dMY and fat yield. Partial linear and quadratic regression coefficients showed an average increase of 4.05 and 0.158 kg of 305-dMY and fat yield, respectively, for each additional day open, and average decrease of 3.58 and 0.017 kg of 305-dMY and fat yield, respectively, for each additional day dry. Mixed model procedures were used to estimate variances and covariance. Heritabilities for 305-dMY, fat, days open and days dry were 0.223, 0.220, 0.018 and 0.067, respectively. Genetic correlations between different traits ranged from -0.129 to 0.958. Phenotypic correlations between different traits ranged from -0.122 to 0.660. A days' open length of 60-90 and dry period length of 60 days were suggested as optimal for attaining maximum lactation milk and fat yields for Friesian cows in Egypt.
A rotal of 21,441 milking records of biweekly test-days were collected from six dairy farms of Almarai company, Saudi Arabia to determine the effect of days open on lactation curve and milk production during the period of 1991 to 1996. These records included cows calved in two seasons: winter, for cows calved from October to March and summer, for cows calved from April to September. Season of calving did not have a significant effect on the last biweekly points of the curve, and this is due to the effect of the evaporative cooling system. Days open had a marked effect on milk production. The difference in milk yield between cows with days open <60 days and days open >150 days was 1,021 liter. Moreover, the difference in milk yield at early lactation decreased from 1,021 to 829 liter as the days open increased from 75 to 125, due to the decrease in the effect of conception on milk production with advancing lactation. These data also showed that the middle parr of the curve (105-255) was the least affected part by the variation in days open because the pregnancy effect become more obvious after five months of conception. These data showed that the dairy cattle produce more than 70% of the milk yield during the first 250 days of the lactation curve.
Article
A total of 1620 lactation records of Friesian cattle from the files of the Ministry of Agriculture farms at Sakha and El _ karada from 1969 to 1979 were used to study relationships of days open and days dry with milk production. The effect of farm, parity, season and year of calving and the possible interactions were also investigated. Open period , days dry , season and year of calving , and farm significantly influenced milk production, while the effects of interactions of farm by parity , farm by season of calving and parity by season of calving were non significant. There was an average increased of 2.2 and 1.4 kg of 305 day and total milk yield, respectively, for each additional days open . A days open length of 60- 90 and dry period length of 60 days were suggested as optimum length for attaining maximum production for Friesian cattle in Egypt. Factors for adjusted 305 day milk yield for various days open length were constructed by smoothed least squares means of days open classes. List of these factors are presented.
Article
Relationships of breeding and manage- ment factors to economic return for dairy cows were studied in lifetime records from 933 Holstein cows. A profit func- tion was defined from milk production, body weight, reproductive performance, herdlife, and prices for feed energy, milk, calves, salvage value, and fixed costs. Statistics on individual cows were milk yield, days in milk for each lactation, fat percent, weight at first calving and matur- ity, number artificial inseminations, and age at each calving and at disposal. Values of each trait maximizing a second trait are defined as optimal. Optimum percent days open and days dry were 31.0 and 10.5 for profit per day-herdlife. Slightly larger percentages were optimal for total performance traits, profit-life, milk-life, and herdlife. Optimum age at first calving for total lifetime performance was 22.5 to 23.5 mo. Profit per day of herdlife was $.05 larger for cows calving during the 25th mo of age than those calving earlier. Days open, days dry, and age at first calving accounted for 10.0, 4.5, and .9% of variation in herdlife; for 4.3, 18.8, and .6% in milk per day-life; and 8.1, 8.3, and 5.2% of variation in profit per day-herd- life. Correlations between age at first calving with percent days open and herd- life were .05 and -.10. Maximum profit per day-herdlife was expected for cows with 25 mo of age at first calving, 124
Article
Full-text available
Prediction equations were determined to estimate daily milk yield from 306 to 395 d in milk for forecasting herd milk sales from Holstein cows in lactation > 305 d. Data were test day milk weights for 65,322 primiparous and 119,220 pluriparous lactations of > 305 d from the Southern US. A forecast model was developed using same lactation 305 d miik yield (in classes of 500 kg incre- ments) that gave similar predicted daily yields as models utilizing last sample milk weight information. This model has the advantage of early forecasting of later milk using projected 305-d yields. Reduced forecast models ignoring days pregnant, yield class, or both accounted for 95, 68, and 59%, and 91, 67, and 56% as much variation in daily milk as the full model for the primiparous and plu-
Article
In order to survey effective factors on economic traits in Montbeliarde and Sarabi cows this study was done. Traits were studied in research include Milk Production (MP), Days In Milk (DIM) and Calving Interval (CI) in Montbeliarde and Sarabi cows. Factors that were putted as variable in models for each trait proportionally include the effect of sire, dam within sire groups, month, season, the year of the calving, lactation number, days open and dry period. Least squares method was used because of unequal observations in subgroups. Model fitting was carried out using restricted maximum likelihood with DFREML. Hentabihty was estimated for milk production of Montbeliarde and Sarabi cows 0.23±0.07 and 0.28±0.09 for Montbeliarde and Sarabi cows days in milk 0.16±0.05 and 0.13±0.06 and for calving interval in Montbeliarde and Sarabi cows was calculated 0.12±0.03 and 0.10±0.04, respectively. Repeatability for milk production in Montbeliarde and Sarabi cows was estimated 0.39 and 0.32, respectively.
Article
Previous and present days open of the first three lactations were fit simultaneously as fixed effects using a mixed model containing herd-year-seasons and groups of sires (fixed effects), sires within groups, and cows nested within sires (random effects). Best linear unbiased estimates showed that, as present days open increased from 20 to 305 d, milk yield increased by 1024, 1221, and 1015 kg and fat yield increased by 30, 39, and 33 kg in first, second, and third lactations, respectively. As previous days open increased from 20 to 305 d, milk yield increased by 1041 and 1097 kg and fat yield increased by 35 and 43 kg in second and third lactations, respectively.Multiplicative adjustment factors were developed to adjust production data for the mainly environmental effects of previous and present days open. Small differences were found between the various sets of factors. One set of factors could be used for all lactations with only small differences in adjusted records.
Article
Cow estimated transmitting abilities (ETA) for milk yield and fat percent derived by best linear unbiased prediction methods were used to compute averages for each herd and year of calving subclass for herds enrolled on the Record of Production program (ROP). Means and variances of herd averages were tabulated according to province, herd size, and year of calving. The genetic trends in herd averages within herd size categories were positive for milk yields and negative for fat percent. The variance of herd averages has increased since 1958 within herd size categories, but has decreased over all herds due to a shift in size of herds since 1958. Herds with fewer than 20 cows represented 31.7% of the ROP herds in Canada in 1977 while in 1958 they represented 72.4%. However, in 1977 the larger herds did not show any genetic advantage over smaller herds. Ontario herds of size 20–9 cows showed greater variability in average ETA for milk and fat percent than herds in other provinces. Correlations among traits on a herd average basis have not changed in the last 10 yr even though herd averages have changed substantially over the same period. Herd genetic differences accounted for only 2.05% of herd phenotypic variance for milk yield and 12.74% for fat percent. Key words: Genetic differences, herds, cow indexing
Article
A range of preplanned dry period lengths in a dairy herd was evaluated, at different culling strategies and feeding regimes, by means of a dynamic stochastic model simulating the production at herd level. Dry period lengths were studied in the range of 4 to 10 weeks. The culling strategies exhibited two different rates of voluntary culling for reproductive failure and milk production, and the feeding regimes consisted of grass silage ad lib. and either 8 or 12 kg of concentrates/day in the first 24 weeks of lactation. The economic result was studied under a herd size and a milk quota constraint, respectively. A dry period of seven weeks appeared to be preferable under most circumstances. The net revenue per unit of milk sold was less sensitive to dry period length than the net revenue per cow per year. No major interactions between dry period length and culling strategy or feeding regime were found. The conclusions were fairly insensitive to price changes, and to variation in the assumed effect on lactational performance of dry period lengths from 6 to 8 weeks.
Article
A 42-mo field trial was initiated in 65 New York Dairy Herd Improvement herds to evaluate the effects of length of dry period on disorders at calving and subsequent milk production. Common disorders and udder edema at parturition were not associated with the length of the preceding dry period. Cows were assigned to treatment group dry periods of 20, 30, 40, 50, and 60 days by modulus 5 of their index numbers. Cows which averaged 10 to 40 days dry produced from 450 to 680 kg less milk in the following lactation than cows with average dry periods of 40 days or longer. Although there was some gain in milk production during the previous lactation from the longer lactation - shorter dry periods, it was less than half the loss in the following lactation. The depressing effect of the short dry periods did not carry over to the second lacta- tion. Cows with dry periods of 40 ___ 10 days produced as much as .cows with 50 days dry or more.
Article
An approximate formula is derived for the variance of intraclass correlation when unequal numbers of observations per group occur. The effect on the variance of t of adding groups with single observations is examined using the formula and results obtained by empirically generating data on a computer. The empirical results indicate that the approximate formula is satisfactory over the range of numbers used. Adding a group with fewer than the average number of observations per group tends to reduce Vt by increasing the degrees of freedom for groups by one, but tends to increase Vt by decreasing the average precision of estimating group means. The net effect can be either negative or positive, depending on t, s and the ni’s. Robertson [1962] pointed out that, when the ratio of the between group mean square to the within group mean square is small, exclusion of groups below half the average size will reduce the variance of the between group component. He further suggested a method for combining estimates of the between group component when n is highly variable. Results using the formula show that the point where efficiency is lost when a group of size one is added is primarily a function of the number per group, and is affected very little by the number of groups. The value of n where groups of size one should be excluded is shown graphically for varying levels of t. Increases in Vt are demonstrated using the empirical data. The empirical results suggest that the increase in V t may be even larger than the formula indicates, especially for large values of t. Only the addition of groups of size one is studied. Adding small groups larger than one would also tend to increase Vtwhen n and t are small.
Article
The IBM-DHIA records of 2,364 cows of four breeds were analyzed to study the effects of breed, season of calving, gestation, preceding dry period, and body weight upon milk, :FCM, and butterfat production in southeastern United States. The total regressions for milk, FC~, and fat were highly significant due to the combined effects of the five variables with 1~ ~ values of 40.5, 31.0, and 24.9%, respectively. Partial regressions of FCM and fat yield on season of calving, gestation, and body weight were significant. The effect of the length of preceding dry period in this study was negligible. Breed differences accounted for 11% of the variation in milk production, 7.4% of the variation in FCM production, but only 3.7% of the variation in fat yield. The effects of breed, season of calving, gestation, preceding dry period, and body weight upon milk and fat production have been studied for many years. The results of these studies have varied with the geographic locations in which they were conducted. Breed differences have been reported to affect milk and fat-corrected milk (FCM) production (3). In 1935, Plum (13) found more within breed variation than he did between breed variation in butterfat pro- duction. In 1960, Fosgate and Welch (3) reported a highly significant between breed variation for milk and FCM, but the variation for butterfat between breeds was small. Gowen (6) reported that body weight in Jerseys was the highest single measurement correlated to milk and fat production. In 1956, Farthing and Legates (2) found no appreciable increase in milk yields with increased body size in Jerseys. In 1925, Wylie (16) pointed out that, if a constant level of feed was maintained throughout the lactation, the influence of season of calving was greatly reduced. Fall-calving cows have been reported as having the highest average production (12, 15). At least two reports have indicated that winter- or spring-calving cows have the highest average pro- duction (3, 7). Inasmuch as disagreement still prevails among researchers as to the effects of breed, season of calving, gestation, preceding dry period, and body weight upon milk and fat production, this study was undertaken to determine the effects of these variables upon milk, FCM, and fat production in the Southeast.
Article
Components of variance are estimated for the three-way classification analysis of variance of DHIA reported first and second milk and fat records of artificially sired Holstein cows and of Owner-Sampler reported milk and fat records of artificially sired Holstein cows. The total variance of milk and fat records is partitioned into the following components with the approximate percent of total variance: sire, 6%; year-season, 2%; herd, 30%; sire by year-season, 0%; sire by herd, 1–2%; herd by year-season, 6–8%; sire by herd by year-season, 1–7%; and residual, 50%.
Article
(2) Service; i.e. the stage of the lactation at which the cow again becomes pregnant. The interval between calving and the next fertile service is here termed the Service Period (S.P.); thus if a cow calves on June 1st, and becomes pregnant again on July 1st, her S.P. for that lactation is 30 days.(Received April 01 1927)
Article
Thesis (Ph. D.)--Ohio State University, 1958. Includes bibliographical references (leaves 49-54).
Article
Vita. Thesis (Ph. D. in Animal Industry)--North Carolina State College. Bibliography: p. 57-62.
Heritabiliry of the length of the sestation oeriod in dairv cattle
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Som6 effecfs of service period and dry period on milk and butterfat production
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Can. J. Anim. Sci. Downloaded from pubs.aic.ca by DALHOUSIE UNIVER on 11/11/13 For personal use only.