Article

# Effects of Days Open on Annualized Milk Yields in Current and Following Lactations

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## Abstract

Length of open period affected annualized yield [(total lactation yield/calving interval) 365]. Yield was maximum with more days open for low, as opposed to high, peak production and for primiparous, as opposed to multiparous, cows. Interactions with days open were not found for mean herd production or cow production relative to the herd mean. Number of days open for maximum yield was similar for milk, fat, and economically fat-corrected milk [.67 kg milk + 10 kg fat]. Correction factors were derived by smoothed least square means of days open classes. Additive adjustment factors were more appropriate than multiplicative adjustment factors. Records adjusted for days open were not able to predict the following lactation yield significantly better than unadjusted records. Cumulative yield of current and following annualized lactations, including the contribution of the calf expressed in units of milk production, was greatest at 117 and 98 days open for primiparous and multiparous cows. For cows with high peak production maximum yield was with 12 to 14 fewer days open than for cows with moderate peak. Conception prior to 2 mo postpartum had an adverse effect on cumulative yield.

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... If pregnant for eight months, corresponding losses were 207, 8.1, 8.7 and 10.7 kg respectively due directly to the effect of pregnancy. 0 1997 Elsevier Science B.V. 1974 Danell, 1982;Weller et al., 1985;Funk et al., 1987; Marti and Funk, 19941, which are assumed to account indirectly for the effect of pregnancy. Although CI and DO are related to the length of the pregnancy in each lactation, the former comprises the combined effect of pregnancy, days open and days dry, each of which has a specific and distinguishable effect on milk yield in dairy cattle (Wood, 1985; Brotherstone, 1987;Funk et al., 1987). ...
... Erb et al. (1952) observed a fourfold increase in rate of decline between day 181 and 223 post conception compared to the earlier stages of gestation. This may explain the difference between our estimate of the effect of pregnancy on total lactation yield and reported additive adjustment factors for equivalent days open (Danell, 1982;Funk et al., 1987;Weller et al., 1985). Direct comparison cannot, however, be made because of the difference in breed and level of production of the cows in these studies. ...
Article
The effect of gestation stage on daily milk production and composition was investigated using first lactation weekly test day records of 325 Holstein Friesian cows in one herd. Gestation stage had a significant effect (P < 0.05) on all traits, accounting for 1.38 to 1.69% reduction in total sum of squares for yield traits and less than 0.4% reduction in total sum of squares for content traits. Decline in daily yield due to pregnancy began from the first month of gestation and increased non-linearly to about 3.0, 0.08, 0.12 and 0.14 kg/day respectively for milk, fat, protein and lactose yield in the 8th month of gestation, corresponding to 7–12% of the mean daily yield. There was little change in protein and lactose content but fat content increased significantly from the 6th month of gestation. A significant interaction between gestation stage and lactation stage was observed, indicating that the adverse effect of pregnancy was higher in mid lactation than in late lactation. Lactation milk, fat, protein and lactose yield was estimated to decline by 21, 1.5, 0.9 and 1.4 kg respectively for cows that were pregnant for three months during lactation. If pregnant for eight months, corresponding losses were 207, 8.1, 8.7 and 10.7 kg respectively due directly to the effect of pregnancy.
... If pregnant for eight months, corresponding losses were 207, 8.1, 8.7 and 10.7 kg respectively due directly to the effect of pregnancy. 0 1997 Elsevier Science B.V. 1974 Danell, 1982;Weller et al., 1985;Funk et al., 1987; Marti and Funk, 19941, which are assumed to account indirectly for the effect of pregnancy. Although CI and DO are related to the length of the pregnancy in each lactation, the former comprises the combined effect of pregnancy, days open and days dry, each of which has a specific and distinguishable effect on milk yield in dairy cattle (Wood, 1985; Brotherstone, 1987;Funk et al., 1987). ...
... Erb et al. (1952) observed a fourfold increase in rate of decline between day 181 and 223 post conception compared to the earlier stages of gestation. This may explain the difference between our estimate of the effect of pregnancy on total lactation yield and reported additive adjustment factors for equivalent days open (Danell, 1982;Funk et al., 1987;Weller et al., 1985). Direct comparison cannot, however, be made because of the difference in breed and level of production of the cows in these studies. ...
Article
The effect of pregnancy on milk yield and composition has long been recognised (Erb, 1952), yet it is not currently directly accounted for in genetic evaluations. In the UK, total lactation yields are adjusted for the effect of calving interval (CI) with adjustment factors (Brotherstone, 1987) which assume a constant effect across gestation stage (GS). The effect of pregnancy however varies with gestation stage (Coulon, 1995) and is different from the effect of CI. In genetic evaluation based on test day models, it is essential to account for the direct effect of pregnancy specific to individual records. The objective of this study was to estimate the effect of gestation stage on daily milk yield and its components in first lactation.
... On the other hand, other studies have demonstrated an advantage for a longer days open (DO) period: Bar-Anan and Soller (1990) reported that in high-yielding herds the highest productivity in the current and subsequent lactations was achieved by Primiparous cows that were inseminated not earlier than 70 days pp and by multiparous cows at 41 to 90 DO. Heimann (1984) advocated prolonged calving intervals, particularly for high-yielding cows with good persistency, whereas Weller et al. (1985) reported that conception before 60 post-partum had an adverse effect on the annualized cumulative milk yield of current and following lactations, and found 110 to130 days DO to be optimal for Primiparous cows. ...
... Bar-Anan and Soller (1990) reported that in highyielding herds the highest productivity in the current and subsequent lactations was achieved by primiparous cows that were inseminated not earlier than 70 days post partum and by multifarious cows at 41 to 90 days open. Heimann (1984) advocated prolonged CI, particularly for highyielding cows with good persistency, whereas Weller et al. (1985) reported that conception before 60 days in milk (DIM) had an adverse effect on the annualised cumulative milk yield of current and following lactations, and found 110 to130 days open to be optimal for primiparous cows. ...
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Dairy buffalo is the major source of milk production kept under peri-urban, low input production system. There is no practice of feeding animals according to production requirements; exposing them to nutritional deficiency with the onset of pregnancy. The onset of pregnancy leads to a decline in milk yield, which compels the farmers to keep the animals un-bred. The present work was completed under four studies to investigate the post-conception decline in milk yield in relation to feeding regime and milk progesterone levels. The overall economic losses due to delayed breeding were also investigated. Study-I, A total of 30912 weekly milk yield records of lactations pertaining to 465 pregnant and 179 non-pregnant buffaloes from three different locations were recorded for 48 weeks. Post conception reduction in milk yield was effected by location, conception season, lactation week, gestation month and parity. Gestation month contributed to the .reduction in milk yield by 1.4%. Parity 3 showed the least reduction followed by parity 2, 4, 1, 5, and 6, indicating it as the best phase for milk production in dairy buffaloes. Under the Study-II reduction in milk yield due to pregnancy was worked out as the difference between milk yield of 23 pregnant and 17 non-pregnant buffaloes, through various models. The buffaloes were provided with three treatments: i) pregnant-ration-traditional (PRT); ii) pregnant-ration-supplemented (PRS) and; iii) non-pregnant-ration-traditional (NPRT). The animals were categorized into HMY; MMY, LMY, producing 66-75, 5665, and 46-55 liters per week, respectively. Milk production was recorded up to 23rd week and the difference in means was worked out. The reduction in milk yield was apparent after 5th week of conception and was significant in 17th week. The line JP8 model (two straight lines with joining point at week 8) gave good fit (R2 = 0.9527) and the predicted values were much closer to the actual. The treatment effect was significant after 6th week post conception. In MMY the supplementation support to milk yield was smaller than the HMY. In LMY buffaloes the decline was drastic in PRT than the other two treatments. In Study-III, Forty adult lactating dairy buffaloes were investigated from 1st to 23rd weeks post-conception at a peri-urban dairy farm in Pakistan. The animals were assigned to three treatments: PRT (pregnant-ration traditional), PRS (pregnant-ration supplemented), NPRT (non-pregnant- ration traditional) and three milk yielding (MY) groups (HMY, high, 66 to 75 liter/wk, n=12; MMY, moderate, 56 to 65 liter/wk, n=16; LMY, low, 46 to 55 liter/wk, n=12). Milk samples were collected on alternate weeks. Milk composition was determined through ultrasonic milk analyzer. EIA (enzyme immunoassay) was used for MPL .Groups means were compared and correlation analysis was conducted. The trends of milk yield as affected by progesterone concentration were analyzed using a regression model based on joining point of the two phases. Differences in MPL became significant among the production groups after 8 weeks of conception. Treatment had a significant effect on MPL. Interaction of production groups was significant with treatments during the 2-8 weeks and with weeks post conception during 10-23 weeks. Treatment x week interaction was significant only during 2-8 weeks. MPL increased in a similar pattern with the advancing weeks post-conception in all the three production groups; however the progesterone levels were slightly but constantly higher in LMY followed by MMY and HMY buffaloes. The HMY and LMY buffaloes showed greater MPL in the supplemented than the animals on traditional ration (P<0.001). MPL correlated positively with fat (%) while negatively with milk yield, protein (%) and lactose contents (%). Decrease in milk yield was mild with the increasing progesterone levels up to 6.44 ng/ml but further increase in the MPL decreased the yield drastically. The PRT animals showed a sharp decline in milk yield with increasing progesterone levels. However, in the PRS animals increasing MPL from 2.0 to 5.84 ng/ml did not affect the milk yield while further increase in MPL resulted in a decrease in milk yield. In Study-IV, Complete milk yield records of 3,304 buffaloes were collected from a group of state farms. Economic traits including lactation yield, lactation length, calving interval (CT), dry period and milk yield per day of calving interval (MYPDCI) were derived from the data. The animals were grouped according to parity number (1-3), service period (GI to G4, conceiving during <150, 150-200, 200-300 and >300 days), respectively and milk yield levels as HMY>2,500; MMY 2,001-2,500; and LMY 1,500-2,000 liters/lactation. The effect of pregnancy on milk composition was investigated in a medium size private dairy farm, using forty lactating buffaloes of three yield levels and four service period groups as described, already. Milk was sampled on the alternate weeks and analyzed for fat and protein contents (%). For quantifying the value of milk produced during a lactation period; the value corrected milk (VCM) was determined and converted to lactation milk value (LMV). Group means were compared for various parameters. Highest milk yield (2,836.50±15.68 liters/lactation) was recorded in the HMY animals of G4 group while lowest milk yield of 1 ,657.04±8.34 liters/lactation was found in LMY of GI. Lactation length was significantly increased with the increasing service period. The shortest dry period was recorded in HMY, parity 1, GI animals and the longest in parity 2, MMY, G4. The CI was shortest in HMY, parity I, and GI animals and longest in LMY, parity 3, G4 buffaloes. The HMY, parity 2, GI buffaloes showed the highest MYPDCT and the lowest value (6.53±0.17 vs 2.76±0.04 liter/day) was recorded for LMY, parity 1, G4 buffaloes. The VCM decreased with the delayed conception. This decreasing trend was higher in respect to the total yield but the decrease in the VCM was smaller due to the increasing levels of fat and protein contents in the milk. The gap among various production classes was reduced while looking at the VCM as compared to the milk yield per day of CI. The LMV showed a consistent decline with the extending service period in all the three production groups. In conclusion, the onset of pregnancy in dairy buffaloes results a drastic decline in milk yield at an early stage and the high milk producers are more sensitive to this decline. Buffalo does not loose her body condition rather decrease her milk yield rapidly than cattle, after the onset of pregnancy. A pregnant animal, if supplemented at the rate of 1 kg ration for every 2 liters of milk will retain milk yield level for a longer duration post- conception. In high milk producers the cost of this supplementation was ten times less than the loss due to milk yield decline after the onset of pregnancy. Increase in MPL with an almost constant linear trend in dairy buffaloes was reported. Concentrates supplementation raised progesterone levels probably through reducing production stress. The critical level of 6.4 ng/ml of MPL caused drastic decline in milk yield while the two parameters also' showed a constant inverse relationship in buffaloes. An animal conceiving at later stages of lactation showed a decline in financial returns by 24-27% than those conceiving earlier.
... Several studies indicated that 12-mo CI is optimal and increased profitability compared with extended CI (Louca and Legates, 1968;Oltenacu et al., 1981;Holmann et al., 1984;Weller and Folman, 1990). On the other hand, some studies demonstrated the benefit of an extended CI (Weller et al., 1985;Arbel et al., 2001). Cumulative yield of the current and subsequent annualized lactations was greatest at 117 and 98 d open for primiparous and multiparous cows, respectively (Weller et al., 1985). ...
... On the other hand, some studies demonstrated the benefit of an extended CI (Weller et al., 1985;Arbel et al., 2001). Cumulative yield of the current and subsequent annualized lactations was greatest at 117 and 98 d open for primiparous and multiparous cows, respectively (Weller et al., 1985). ...
... We computed days open as described by Weller et al. (1985), and all 3 DO terms were required to accurately describe the effect of days open on production traits. For cows that were not pregnant, DO = 0, and the expected increase in production was included in the P m effect. ...
Article
The objective was to test the hypothesis that more frequent but less accurately analyzed milk components may give a more representative measure of a cow's total lactation production. Daily records for milk production and fat and protein concentration collected by the AfiLab recording system (Afimilk, Kibbutz Afikim, Israel) from January 2014 to January 2016 from 47 large kibbutz (communal) herds distributed throughout Israel with a total of 37,486 Israeli Holstein cows were compared with the same statistics derived from monthly test day records derived by Bentley and Foss milk analyzers at the central laboratory of the Israel Cattle Breeders Association. The lactation means for all traits were quite similar for the 2 methods in both parities, except for fat production, which was lower for the daily records. This finding corresponded to fat lactation curves, which showed that daily results were lower with low days in milk (DIM) but almost equal to the monthly results after 125 DIM. Relative to monthly records, daily records overestimated protein percentage before 150 DIM and underestimated protein percentage in the second half of the lactation. The standard deviation for first- and second-parity daily records scored by the monthly and daily system were least similar for fat percentage, but even for this trait the difference was no more than 0.1 percentage points. The standard deviations for complete lactation production were slightly lower for the daily results for all traits but protein production. First-parity heritabilities were higher for lactations computed from daily records for all traits except for protein percentage, but differences were not significant. For daily records, coefficients of determination to predict future milk, fat, and protein lactation production from truncated lactations were greatest and root mean squared errors were least if the mean production from the last 2 weeks before the truncation date was used to estimate future production. Daily first-parity partial lactations for milk, fat, and protein production with <150 DIM predicted future lactation more accurately than corresponding monthly partial lactations. With only 30 DIM, genetic correlations between predicted and actual lactations ranged from 0.73 to 0.79 for milk, fat, and protein production. Real-time daily recording of fat and protein concentration by the daily recording system may be preferable to monthly analysis for herd-management decisions and genetic evaluation. Further study is required to compare the results of individual cows in multiple lactations.
... On the other hand, other studies have demonstrated an advantage for a longer DO period: Anan and Soller (1990) reported that in high yielding herds the highest productivity in the current and subsequent lactations was achieved by primiparous cows that were inseminated not earlier than 70 d postpartum (pp) and by multiparous cows at 41 to 90 DO. Heimann (1984) advocated prolonged calving intervals, particularly for high yielding cows with good persistency, whereas Weller et al. (1985) reported that conception before 60 DIM had an adverse effect on the annualized cumulative milk yield of current and following lactations, and found 110 to130 d DO to be optimal for primiparous cows. Some reasons for the conflict among the results of these studies may lie in the differing criteria and time periods used, yield levels, and the seasonality of production patterns. ...
Article
A field trial was conducted to examine the effect of extended calving interval (CI) on production and profitability of high yielding cows (n = 937). First insemination was performed at 154 and 93 d postpartum (pp), for treatment and control primiparous cows, respectively, and at 124 and 71 d pp for treatment and control multiparous cows, respectively. During the first experimental lactation, average daily value-corrected milk (VCM) yield was 28.5 and 27.7 kg/d of CI for treatment (n = 131) and control (n = 133) primiparous cows, respectively. No significant difference in average daily VCM yield (33.0 and 32.8 kg/d of CI) was found between treatment (n = 271) and control (n = 215) multiparous cows . In the first 150 d of the subsequent lactation, there were significant differences in milk and VCM production in favor of the treatment primiparous cows (41.4 vs. 39.7 kg of VCM/d) but no significant differences in the production of multiparous cows. Primiparous and multiparous cows with extended lactations were more profitable. During the first experimental lactation, there were advantages of $0.19 and$0.12/d of CI in the net returns for primiparous cows and multiparous cows with longer CI, respectively. When the economic analysis included the first experimental lactation plus the first 150 d of the subsequent one, the net return per day of CI was higher for cows with an extended voluntary waiting period: $0.21/d and$0.16/d for primiparous and multiparous cows, respectively. A delay of 60 d with respect to the usual voluntary waiting period in the beginning of inseminations of high yielding cows has economic advantages and allows the farmer an option for decisions regarding individual cows.
... One of the most important reasons for the decrease in fertility of cows is a silent estrus leading to some considerable economical losses caused by the elongation of inter-pregnancy period. From the research by Weller et al. (24) it may be concluded that fertilization before 60 days after calving negatively influences milk yield not only in the current but in the consecutive lactation as well. Moreover, it was demonstrated that in the case of high producing cows there is a phenomenon of the spontaneous elongation of the interval to the occurrence of the first estrus after calving, caused by the energy deficiency during the period of increasing milk yield, that is in some manner a form of self-defense against premature pregnancy (4,7). ...
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The research involved 432 cows, with an average yield of about 10 000 kg of milk in 305-day lactation, kept on a dairy cattle farm in south-western Poland. The aim of the work was a comparison of reproductive and economical features (EJR index - economischjaarresultaat - from Dutch) of Polish Holstein-Friesian breed cows of Black- and Red-White variety with a different contribution of genes of Holstein-Friesian (HF) breed cattle, after the first five calvings. The genotype of cows had a statistically significant influence (p ≤ 0.05, p ≤ 0.01) on the value of sexual rest, inter-pregnancy and inter-calving periods, and also the economical value expressed as the EJR index. It also significantly differentiated the magnitude of the fecundation index and sexual rest period, and economic value of the analyzed groups of cows. In cow herds, especially of Black-White breeds with a high contribution (> 87.5%) of HF cattle genes, the elongated sexual rest, inter-pregnancy and inter-calving periods, poorer survivability until subsequent calvings, and higher economical value (in euro) than in the case of their Red-White age mates should be expected. In heifer cows of high milk yield, lower reproductive feature indices (inter-pregnancy and inter-calving periods, fecundation index) and poorer economical value (EJR index) than in multiparous cows should be expected.
... BarAnan & Soller (1979), studied total productivity over current and following lactations, and found that maximum production was achieved by inseminating primiparous cows not earlier than 70 days postpartum and multiparous at 41 to 90 days postpartum. Furthermore, Weller, Anan & Osterkorn (1985), stated that the period between calving and insemination affected the milk yield. Cumulative yield of current and following annualised lactations, was greatest at 117 and 98 days open for primiparous and multiparous cows, respectively. ...
Article
The general aim of the present work was to investigate the opportunities for a planned extended calving interval (CI) in dairy cattle, and how it would effect production and animal welfare. Furthermore, the effects of combining an extended calving interval with an increased milking frequency (MF) was evaluated. The milk production per cow has increased dramatically during recent decades. In thirty years average milk production per cow has increased by more than 3000 kg energy corrected milk (ECM), and the development towards still higher milk yields does not appear to be stopping. High milk yields in combination with a minimised CI results in high yields when drying off, problems at the onset of the lactation and bad utilisation of the milk production capacity of the cow. The current management methods for high producing cows also results in a short length of life and must be questioned, both from an ethical and economical point of view. In total, 72 cows of the Swedish Red and White Breed were introduced to the study, which lasted for three years. There was one conventional CI of 12 months, and one extended CI of 18 months, both of which were tested in combination with two different MF’s, 2x and 3x per day. The groups are referred to as 12-2, 12-3, 18-2 and 18-3. The results presented here show that cows with 18 months CI have as high production, expressed as ECM/day of calving interval, as cows with a 12 months CI and cows in group 18-3 had the highest ECM/day of CI of all groups. An extension of the CI resulted in better feed efficiency compared to the conventional system, and the contents of somatic cells were desirably low throughout the extended lactation. The primiparous cows maintained their production better than the multiparous cows, and an increased milking frequency may contribute to increased comfort in high producing dairy cows. A system with an extended CI, is a less intensive system with fewer risk periods for the cow, and therefore it would increase not only the production, but also the animal welfare and the lifetime of the cow.
... Bar-Anan and Soller (1979) found that maximum production was achieved by inseminating primiparous cows not earlier than 70 days postpartum and multiparous 41 to 90 days postpartum. Weller et al. (1985) stated that the period between calving and insemination affected the milk yield. Arbel et al. (2001) found in their study, that there was an economic advantage in extending lactations by 60 days in high-yielding cows. ...
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Two experiments were performed in two different herds to determine if utilizing prostaglandin F2α to induce estrus for first services would be effective in reducing the duration and variability of calving intervals. In Experiment 1, cows were assigned randomly as controls (n = 217) to be inseminated as they were detected in estrus (beginning d 42 to 53 postpartum depending on replicate) or treated with prostaglandin F2α (n = 185). In Experiment 2, the same treatments were utilized, except control cows (n = 124) were inseminated at their first detected estrus after d 40 postpartum, and treated cows received either one injection of prostaglandin F2α between d 54 and 63 (n = 116) or were given progesterone (via a progesterone-releasing intravaginal device) for 7 d, with the device removed 24 h after prostaglandin F2α (n = 116). More cows were inseminated and pregnancy rates were higher within 5 d after treatment with prostaglandin F2α and interval from prostaglandin F2α to first service was reduced compared with that of control cows. Duration and variation of calving intervals were unaffected in either experiment, despite the fact the elective waiting period was 6 to 23 d longer for treated cows than for controls. Prebreeding treatment with progesterone failed to improve conception rates, but the efficiency of estrous expression increased from 54% in prostaglandin F2α-treated cows to 71% in those cows also receiving prebreeding progesterone. We conclude that prostaglandin F2α was ineffective in improving reproductive performance of these herds undergood herd management. However, prostaglandin F2α offers the convenience of inseminating small groups of cows, controlling when breedings occur during the work week, and prolonging the elective waiting period without extending the calving interval.
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The aim of the study was to evaluate the relation between calving interval length, milk yield, milk components, insemination index and health of high yielding cows. The experiment was carried out on 90 HF cows, divided into 2 groups (45 cows in each), according to the analogue method. The cows in the 1st group were inseminated for the first time on day 42 and in the 2nd group on day 120 following calving. During the whole period the cows were kept in a loose barn with an outside run and fed a complete TMR diet (total mixed ratio) consisting of conserved feed according to the INRA-system. Milk samples were taken from each cow once a month during the whole lactation period. The amount of milk and the concentration of fat, protein and lactose were estimated. Contrary to expectations, the average length of period from calving to conception in the 1st and 2nd groups was (respectively): 111.4 and 163.4 days. The milk yield of the cows in group 2 was higher by 150 kg per 305-days lactation (the difference was not significant). There were also no significant differences in composition. The only significant difference was in the lactose concentration of the milk from the cows belonging to the 2nd group and it may be concluded that the energy balance in the bodies of these cows was better. During the whole lactation period the average daily milk yield of the cows in group 2 was 0.5 kg higher than in group 1. There were no differences in the insemination index between both groups. The percentage of mastitis and metabolic disease was lower in the 2nd group of cows.
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A total of 2302 high-yielding cows from the active population used in Pomerania and Kujawy regions were analyzed for milk yield, fertility and culling levels. Lifetime performance of the cows (lifetime milk yield in kg, life span, length of productive life, milking days, milk yield per day of life (utilization), mean calving interval (CI), number of calvings and number of calves born alive) was estimated according to the length of the first calving interval (≤340, 341-370, 371-400, 401-430, 431-460, 461-490 and >490 days). It was found that excessive shortening of the first calving interval in high-yielding cows was an error resulting in significant losses in the form of reduced first lactations and lifetime milk yields. It is debatable whether the first calving period should be lengthened. This had a favorable effect on the yield of first calvers (r = 0.6xx), but had no statistically significant effect on lifetime milk yield (r = 0.01) or length of productive life (r = 0.01). The length of the first CI was negatively and significantly correlated with the number of calvings and the number of live born calves. The group of cows with the longest first CI included cows with the lowest fertility, indicating that their mean CI was very long. As the first CI increased even up to 490 days, some parameters of cows' lifetime performance (such as lifetime milk yield, life span and length of productive life) tended to increase slightly, but lengthening the period of productive life was not directly proportional to the increase in the lifetime number of milking days, because this was accompanied by the lengthening of the dry periods.
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The aim of this study was to evaluate the cumulative consequences of calving interval length in cows on milk yield, its chemical composition and some reproductive traits in second standard and extended lactation. The experiment was carried out on 90 HF cows, divided into 2 groups (45 cows in each), according to the analogue method. The cows in group 1 were inseminated for the first time after 42 days and in the 2nd group after 120 days following the previous calving. The cows were kept in a loose barn during the whole period with an outside run and fed a complete TMR diet (total mixed ratio) according to the INRA system. During the whole experimental period milk samples were taken from each cow once a month for the whole duration of lactation. The amount of milk and the concentration of fat and lactose were estimated. Contrary to expectations, the average length of period from calving to conception in the 1st and 2nd groups was (respectively): 106 and 149 days. There were no differences in the insemination indexes between both groups. The percentage distribution of these indexes was more profitable in the cows belonging to the 1st group. Based on this data it can be stated that cows producing about 9000 kg of milk per 305-d lactation should be inseminated approximately 110 days after calving. The less profitable index insemination in cows from the 2nd group was compensated by a 297 kg increase in milk yield (the differences were not significant). There were no differences in fat and protein percentages and their yield per lactation. The percentage of mastitis was lower in the 2nd group of cows. The results obtained in this experiment indicated that the optimum length of calving intervals in cows producing about 9000 kg milk per lactation should be about 110 days.
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Days open, days dry, and season of calving were examined to maximize Income Over Feed Cost (IOFC) and 305-d mature equivalent milk production for three different production levels. Models with all fixed effects were analyzed using SAS® PROC GLM for 50,743 Holstein cows from 4687 herds calving in yr 1990 and 1991. Production level of cow was not important to determine optimum days open to maximize 305-d milk yield, but was important for days open to maximize IOFC. For 305-d milk yield, days open of 91 to 105 d, 76 to 90 d, and 61 to 75 d were optimum for cows calving in season 2 (February through April), season 3 (May through July), and season 4 (August through October) respectively. For IOFC, optimum days open was 15 d higher for average and above average production levels for seasons 2 and 3 than for below average production level. Optimum days open to maximize IOFC for calving season 4 was 15 d higher for above average production level than for below average and average levels. Cows calving in season 2 had highest optimum days open. Conclusive results could not be obtained for season 1 as less than 10% of records in the data set belonged to that season and of those only 10% had an open period shorter than 150 d. On average, cows calving in season 3 yielded highest IOFC, which was $667,$482, and \$276 more than cows calving in season 1 (November to January), season 2, and season 4 respectively. The 305-d milk yield was not different for the four seasons of calving.
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The financial implications of delays in conception at different stages of lactation in the average and the high yielding dairy cows were investigated. Variables included in the calculations were net loss in annual yield, lost income from a calf, cost of extended dry period, cost of slipping in calving pattern, cost of extra veterinary treatments and AI services, benefit of a delay in calving for reduced risk of production diseases, potential benefit of delay in conception on milk yield from the current lactation, and the value of quota leasing. For the average yielding cow, the net cost of one day of delay in conception was calculated at £2.41 when conception is delayed from 85 to 100 days post-calving, increasing to £5.02 per day if conception occurred at 146 to 175 days post-calving. After taking value of quota leasing into account, the net cost of a lost day was calculated at £1.73 and £3.55 per day for the two delay intervals respectively. For the high yielding cow, the net cost of one day of delay in conception was calculated at £2.48 when conception is delayed from 85 to 115 days post-calving, increasing to £6.52 per day if conception occurred between 206 and 235 days post-calving. The net costs after quota leasing being considered were calculated at £1.68 and £4.08 per day for the two delay intervals respectively. On the basis of the above estimations, and after considering the cost of culling for poor fertility, it was concluded that it is a cost-effective option to keep trying to get the typical average cow in calf until 266 days post-calving, whereas the breakeven point for the high yielding cow is at 290 days post-calving.
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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.
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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.
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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.
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The relationships between days open, days dry, and 90-day and 305-day production were studied, using 4,385 lactation records from nine North Carolina Institutional Holstein herds from June, 1950, through December, 1958. Relationships were studied separately for first, second or later, and all lactations to determine if adjustment of 305-day lactation records for days open and days dry are warranted in compiling sire summaries. The intra-herd-year-season phenotypic correlations between 90-day production and days open were not significant and ranged from 0.05 to 0.08, suggesting that level of production had very little influence on this meeasure of fertility. The heritability estimates for days open were also very low, ranging from 0.01 in first lactations to 0.09 for all records. Length of the previous dry period had very little influence on production, accounting for only 0.6 and 0.3% of the variation in 90-day and 305-day fat yield and less than 0.1% of the variation in the two measures of milk production. Number of days open during the lactation significantly influenced production and accounted for 6.5, 4.3, and 4.2% of the variation in 305-day milk yield for first, second or later, and all lactations, respectively. Factors for adjusting 305-day production for differences in days open are presented.
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Models for developing adjustment fac- tors for days open, effects of alternative methods to evaluate lactation yields, and effects of alternative methods of mea- suring yield on sire evaluation were inves- tigated. Effects of days open on produc- tion were reduced by including summit production (average of 2 highest of first 3 test days) in models; however, adjust- ment of records by factors from models including summit production were not satisfactory for records with greater than 180 days open. Annualized yield ((total lactation production divided by days between calvings) 365) overcompensated for days open greater than 180. Days open adjusted, annualized yield, and fat- corrected yield were closely correlated. Mature-equivalent production in first parity was most predictive for yield in second parity, but yield adjusted for days open was more predictive of total cumu- lative yield at 26, 39, and 52 too. Rank correlations among sire trans- mitting abilities computed from alterna- tive measures were more than .86. Evalua- tions by yield adjusted for days open were most similar and fat-corrected yield least similar to evaluation by mature equivalent production. Changes in culling decisions and sire evaluation from use of annualized yield or yield adjusted for days open versus mature equivalent were small, and yield adjusted for days open is preferred over annualized yield.
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Holstein lactation records from New York Dairy Records Processing Labora- tory were used to estimate relation- ships between days open and cumulative milk yield at intervals from parturition and the effect of lactation number, season of freshening, and production on these relationships. The relationship of days open with total days in milk also was estimated. Quadratic regression equations that relate cumulative milk yield at 210, 240, 270, 300, 330, and 360 days from parturition and total number of days in milk with days open were estimated for cows with high and low yields in first, second, and third and later lactation freshening in three seasons. Milk yield early in lactation was used to classify cows in classes of high and low production. The association between days open and cumulative milk yield was less for cows within a production class than across all cows with production early in lactation ignored. The change in cumulative milk yield at 305 days associated with number of days open was greater for older cows than for cows in first lactation but not different between high and low producing cows within lactation. This indicates that correcting 305-day milk yield to a standard number of days open should be additive. Quantities of milk required to correct milk production to a standard 100 days open were calculated.
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Losses in milk yield due to delayed breed- ing were determined frmn 4,910 complete lactations of Holsteins in the North Caro- lina Institutional Breeding Association. Production of 756 cows to the end of the lactation terminating nearest 48 months after first calving was utilized in the first phase of the study. Regression analyses within herd and year of first calving with age at calving, total days dry, and total days in milk as covariates, revealed a quadratic relationship between days open and production. There was an average decrease of 2.40 ± 1.09 kg of milk and 0.112 ± 0.040 kg of fat for each addi- tional day open. A parallel study utilizing shorter production intervals included 1,580 cows with first and second lactations, 1,050 cows with second and third lactations, and 700 cows with third and fourth lactations. Regression analyses were within herd-year- season of calving, with age at calving, days open, and days dry as eovariates. Yields per day for the interval from 210 days after calving through 305 days o2 next lactation, were used as dependent variables. Days open were not uniformly expensive for all lactations of an animal. An increase of 1.16 kg of milk for each additional day open was obtained for first lactations. For second and third lactations there was a decline of 3.58 and 3.68 kg of milk, re- spectively, for each additional day open. The differential response for the first lac- tations was attributed to their higher per- sistency. A calving interval of 13 months for first ealvers and )2 months for second and later ealvers was suggested as an opti- mum length for attaining nmximum pro- duction. Considering the reduced calving rate, as well as the loss in milk yield, net decrease in income for each additional day
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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.
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The effect of season on milk yield, milk composition, oestrus manifestation, oestrus cycle characteristics and conception rate was studied in high-yielding Israeli-Friesian cows. ‘Summer’ cows were allotted to control (SC) and forced ventilation (SV) groups. ‘Winter’ cows (W) were kept in one group. During July-September mean rectal temperatures at 16.00 h in primiparous and multiparous cows were 39·6 and 39·8°C, respectively in cows of the SC group, and 39·4 and 39·3°C, respectively in cows of the SV group. Mean rectal temperatures at 16.00 h of the animals in the W group during December-March were 38·9°C in both primiparous and multiparous cows. The mean 122-d milk yields in primiparous cows were 3508, 3251 and 3571 kg/cow in the SC, SV and W groups respectively (not significant (NS)). In the multiparous cows the respective yields were 4183, 4416 and 4538 kg/cow ( P < 0·05). Differences in milk composition were small and statistically NS. Observations on oestrus manifestation, performed 4 times daily, indicated that standing oestrus lasted 9·2 and 10·6 h in primiparous and multiparous cows respectively ( P < 0·05); differences between groups were statistically not significant. Oestrous cycle lengths of primiparous and multiparous cows were 21·1 and 22·5 d respectively ( P < 0·05) between ovulations and 23·0 and 28·05 d respectively ( P < 0·01) between standing heats. Cows were inseminated following standing heat only. Conception rates (on all services within experimental periods) in primiparous cows were 50, 35 and 72% in the SC, SV and W groups respectively (NS). In the multiparous cows, the respective rates were 22, 52 and 80% ( P < 0·05). It is concluded that in the present experiment hyperthermy decreased milk production to a very small extent, in spite of very high milk yields, but fertility was severely affected. It is also suggested that primiparous cows are less affected by heat stress than multiparous cows.
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In three experiments 250 high-yielding dairy cows were fed for 18 weeks after parturition either a low-protein (LP) diet containing 150 to 160 g crude protein per kg or a high-protein (HP) diet containing 190 to 200 g crude protein per kg. In all three experiments cows were fed an average of 2·6 to 2·9 kg crude protein per day on the LP diet and 3·3 to 3·7 kg crude protein per day on the HP diet. Inclusive of maintenance, crude protein intake was, on average, 71 to 83 g crude protein per kg milk on the LP diet and 84 to 112 g crude protein per kg milk on the HP diet.Protein intake did not affect the post-partum decrease in body weight; however, cows in their 4th and later lactations lost significantly more weight than cows in their 2nd and 3rd lactations (P < 0·01). Number of lactation did not affect the levels of rumen fluid ammonia or plasma urea, but older cows had significantly higher milk yields than younger ones. In all the experiments the first oestrus was observed, on average, between 38 and 43 days after parturition. The first insemination was carried out, on average, between 69 and 75 days after calving. Protein intake or age did not affect the intervals between parturition and the first observed oestrus or insemination. Proportional conception rates of cows fed the LP and HP diets were 0·566 and 0·431, respectively (P < 0·05). Conception rates of cows in their 2nd and 3rd lactations were 0·582 and 0·515 for cows on the LP and HP diets, respectively, whereas conception rates of cows in their 4th and later lactations were 0·526 and 0·288, respectively (P < 0·02). Within the HP-fed group the difference in conception rate between cows in their 2nd and 3rd lactations and those in their 4th and later lactations was also significant (P < 0·01). The proportion of cows pregnant 126 days after parturition was 0·786 and 0·645 for cows fed the LP and HP diets, respectively (P < 0·05). The proportion of cows in their 2nd and 3rd lactations which were pregnant, was 0·792 and 0·702 for cows of the LP and HP groups, respectively. Pregnancy rates for cows in their 4th and later lactations were 0·769 and 0·515 in the LP and HP groups, respectively (P < 0·05).
Article
The effects of days-open on milk yields in current lactations and in following lactations were estimated from 71 911 current and 68 693 following lactation records. Yields were expressed as 305-day, total and annual records, where annual record = 365 × (total yield/days between calvings). The data were grouped according to current days-open, corrected for initial yield differences and analysed separately for heifers and cows in Moshav (moderate-yielding) and Kibbutz (high-yielding) herds. Current 305-day records increased by 15 to 18 kg milk/day-open up to 90 days-open, and 2 to 3 kg/day-open thereafter. In contrast, the effects of increasing days-open on annual yields were generally small and negative, being positive only for heifers up to 90 days-open. Thus 305-day records heavily under-rated annual yields of fertile cows. For current lactations, 70 to 100 days-open for heifers and 30 to 50 days-open for cows resulted in the highest annual production. Yields in following lactations were positively associated with days-open in the previous lactation. The effect was highest in high-yielding herds, suggesting that high-yielding cows respond positively to some rest between calvings. Combining the effects of days-open on current and following lactation yields and on the calf crop: in high-yielding herds heifers had the highest productivity when mated not earlier than 70 days post partum , while in moderately-yielding herds days-open did not affect productivity. Cows in high-yielding herds achieved highest productivity at 41 to 90 days-open, while cows in moderately-yielding herds were most productive when mated as early as possible. A comparison of the economic value of sire fertility and sire transmitting ability for milk production showed that fertility may often be over-rated.