• Asian-Australasian Journal of Animal Sciences
• /
• 제19권12호
• /
• pp.1696-1701
• /
• 2006

A random regression model was applied for the first time for the analysis of test day records and to study the genetic persistency of first lactation milk yield of Indian Murrah buffaloes. Wilmink's Function was chosen to describe the shape of lactation curves. Heritabilities of test day milk yield varied from 0.33 to 0.58 in different test days. The highest heritability was found in the initial test day ($5^{th}$ day) milk yield. Genetic correlations among test day milk yields were higher in the initial test day milk yield and decreased when the test day interval was increased. The magnitude of genetic correlations between test day and 305 day milk yield varied from 0.25 to 0.99. The genetic persistencies of first lactation milk yield were estimated based on daily breeding values using two methods. $P_1$ is the genetic persistency estimated as a summation of the deviation of estimated daily breeding value on days to attain peak yield from each day after days to attain peak yield to different lactation days. $P_2$ is the genetic persistency estimated as the additional genetic yield (gained or lost) from days to attain peak yield to estimated breeding value on different lactation days relative to an average buffalo having the same yield on days to attain peak yield. The mean genetic persistency on 90, 120, 180, 240, 278 and 305 days in milk was estimated as -4.23, -21.67, -101.67, -229.57, -330.06 and -388.64, respectively by $P_1$, whereas by $P_2$ on same days in milk were estimated as -3.96 (-0.32 kg), -23.94 (-0.87 kg), -112.81 (-1.96 kg), -245.83 (-2.81 kg), -350.04 (-3.28 kg) and -407.58 (-3.40 kg) respectively. Higher magnitude of rank correlations indicated that the ranking of buffaloes based on their genetic persistency in both methods were similar for evaluation of genetic persistency of buffaloes. Based on the estimated range of genetic persistency three types of genetic persistency were identified. Genetic correlations among genetic persistency in different days in milk and between genetic persistencies on the same day in milk were very high. The genetic correlations between genetic persistency for different days in milk and estimated breeding value for 305 DIM was increased from 90 DIM to 180 DIM, and highest around 240 DIM which indicates a minimum of 240 days as an optimum first lactation length might be required for genetic evaluation of Indian Murrah buffaloes.

• Asian-Australasian Journal of Animal Sciences
• /
• 제25권8호
• /
• pp.1073-1082
• /
• 2012

We first sought to clarify the effects of discounted rate, survival rate, and lactation persistency as a component trait of the selection index on net merit, defined as the first five lactation milks and herd life (HL) weighted by 1 and 0.389 (currently used in Japan), respectively, in units of genetic standard deviation. Survival rate increased the relative economic importance of later lactation traits and the first five lactation milk yields during the first 120 months from the start of the breeding scheme. In contrast, reliabilities of the estimated breeding value (EBV) in later lactation traits are lower than those of earlier lactation traits. We then sought to clarify the effects of applying single nucleotide polymorphism (SNP) on net merit to improve the reliability of EBV of later lactation traits to maximize their increased economic importance due to increase in survival rate. Net merit, selection accuracy, and HL increased by adding lactation persistency to the selection index whose component traits were only milk yields. Lactation persistency of the second and (especially) third parities contributed to increasing HL while maintaining the first five lactation milk yields compared with the selection index whose only component traits were milk yields. A selection index comprising the first three lactation milk yields and persistency accounted for 99.4% of net merit derived from a selection index whose components were identical to those for net merit. We consider that the selection index comprising the first three lactation milk yields and persistency is a practical method for increasing lifetime milk yield in the absence of data regarding HL. Applying SNP to the second- and third-lactation traits and HL increased net merit and HL by maximizing the increased economic importance of later lactation traits, reducing the effect of first-lactation milk yield on HL (genetic correlation ($r_G$) = -0.006), and by augmenting the effects of the second- and third-lactation milk yields on HL ($r_G$ = 0.118 and 0.257, respectively).

• Asian-Australasian Journal of Animal Sciences
• /
• 제15권3호
• /
• pp.315-320
• /
• 2002

Test-day records (n=13677) sampled from 896 ewes in 5-9 (${\mu}$=7.5) monthly test-days were used to estimate genetic and phenotypic parameters of test-day yields, lactation milk yield (TMY), length of the milking period (DAYS) and three measures of persistency of milk yield in Boutsico dairy sheep. Τhe measures of persistency were the slope of the regression line (${\beta}$), the coefficient of variation (CV) of the test-day milk yields and the maximum to average daily milk yield ratio (MA). The estimates of variance components were obtained under a linear mixed model by restricted maximum likelihood. The heritability of test-day yields ranged from 0.15 to 0.24. DAYS were found to be heritable ($h^2$=0.11). Heritability estimates of ${\beta}$, CV and MA were 0.15, 0.13, 0.10, respectively. Selection for maximum lactation yields is expected to result in prolonged milking periods, high rates of decline of yields after peak production, variable test-day yields and higher litter sizes. Selection for flatter lactation curves would reduce lactation yields, increase slightly the length of the milking period and decrease yield variation as well as litter size. The most accurate prediction of TMY was obtained with a linear regression model with the first five test-day records.

• Asian-Australasian Journal of Animal Sciences
• /
• 제24권5호
• /
• pp.610-615
• /
• 2011

We examined the correlations between lactation curve shape, including persistency and changes in body condition score (BCS) during early-stage (0 to 30 days in milk (DIM)), nadir-stage (31 to 90 DIM), and late-stage (91 to 240 DIM) lactation in 191 first-lactation cows. Data used were first-parity BCS records, scored twice every month after calving, and daily milk yields. Individual lactation curves were depicted by the Wilmink function. Lactation persistency was defined as the difference in estimated milk yields between 240 DIM and 60 DIM. Changes in BCSs in the early and late stages were defined as linear regression coefficients. There were no significant correlations between traits for lactation curve shape and change in BCS in early-stage lactation. Peak yield and total milk yield were negatively correlated with BCSs in nadir- and late-stage lactation and with BCS change in late-stage lactation, suggesting that cows with high lactation yields had low body reserves and health status in mid- to late lactation and had delayed recovery of body reserves. Lactation persistency was positively correlated with change in BCS in late-stage lactation, suggesting that cows with high lactation persistency tended to be healthy and to recover their body reserves well in late lactation.

• Animal Bioscience
• /
• 제35권10호
• /
• pp.1499-1511
• /
• 2022

Objective: This study was aimed to estimate the genetic parameters, including genetic and phenotypic correlations, of milk yield, lactation curve traits and milk composition of Thai dairy cattle from three government research farms. Methods: The data of 25,789 test-day milk yield and milk composition records of 1,468 cattle from lactation 1 to 3 of Holstein Friesian (HF) and crossbred HF dairy cattle calved between 1990 and 2015 from three government research farms in Thailand were analysed. 305-day milk yield was estimated by the Wood model and a test interval method. The Wood model was used for estimating cumulative 305-day milk yield, peak milk yield, days to peak milk yield and persistency. Genetic parameters were estimated using linear mixed models with herd, breed group, year and season of calving as fixed effects, and animals linked to a pedigree as random effects, together with a residual error. Univariate models were used to estimate variance components, heritability, estimated breeding values (EBVs) and repeatability of each trait, while pairwise bivariate models were used to estimate covariance components and correlations between traits in the same lactation and in the same trait across lactations. Results: The heritability of 305-day milk yield, peak milk yield and protein percentage have moderate to high estimates ranging from 0.19 to 0.45 while days to peak milk yield, persistency and fat percentage have low heritability ranging from 0.08 to 0.14 in lactation 1 cows. Further, heritability of most traits considered was higher in lactation 1 compared with lactations 2 and 3. For cows in lactation 1, high genetic correlations were found between 305-day milk yield and peak milk yield (0.86±0.07) and days to peak milk yield and persistency (0.99±0.02) while estimates of genetic correlations between the remaining traits were imprecise due to the high standard errors. The genetic correlations within the traits across lactation were high. There was no consistent trend of EBVs for most traits in the first lactation over the study period. Conclusion: Both the Wood model and test interval method can be used for milk yield estimates in these herds. However, the Wood model has advantages over the test interval method as it can be fitted using fewer test-day records and the estimated model parameters can be used to derive estimates of other lactation curve parameters. Milk yield, peak milk yield and protein percentage can be improved by a selection and mating program while days to peak milk yield, persistency and fat percentage can be improved by including into a selection index.

• Asian-Australasian Journal of Animal Sciences
• /
• 제28권10호
• /
• pp.1407-1418
• /
• 2015

A total of 32,817 test-day milk yield (TDMY) records of the first lactation of 4,056 Girolando cows daughters of 276 sires, collected from 118 herds between 2000 and 2011 were utilized to estimate the genetic parameters for TDMY via random regression models (RRM) using Legendre's polynomial functions whose orders varied from 3 to 5. In addition, nine measures of persistency in milk yield ($PS_i$) and the genetic trend of 305-day milk yield (305MY) were evaluated. The fit quality criteria used indicated RRM employing the Legendre's polynomial of orders 3 and 5 for fitting the genetic additive and permanent environment effects, respectively, as the best model. The heritability and genetic correlation for TDMY throughout the lactation, obtained with the best model, varied from 0.18 to 0.23 and from -0.03 to 1.00, respectively. The heritability and genetic correlation for persistency and 305MY varied from 0.10 to 0.33 and from -0.98 to 1.00, respectively. The use of $PS_7$ would be the most suitable option for the evaluation of Girolando cattle. The estimated breeding values for 305MY of sires and cows showed significant and positive genetic trends. Thus, the use of selection indices would be indicated in the genetic evaluation of Girolando cattle for both traits.

• Asian-Australasian Journal of Animal Sciences
• /
• 제19권7호
• /
• pp.915-921
• /
• 2006

Various random regression models with different order of Legendre polynomials for permanent environmental and genetic effects were constructed to predict future milk yield of Holstein cows in Korea. A total of 257,908 test-day (TD) milk yield records from a total of 28,135 cows belonging to 1,090 herds were considered for estimating (co)variance of the random covariate coefficients using an expectation-maximization REML algorithm in an animal mixed model. The variances did not change much between the models, having different order of Legendre polynomial, but a decreasing trend was observed with increase in the order of Legendre polynomial in the model. The R-squared value of the model increased and the residual variance reduced with the increase in order of Legendre polynomial in the model. Therefore, a model with $5^{th}$ order of Legendre polynomial was considered for predicting future milk yield. For predicting the future milk yield of cows, 132,771 TD records from 28,135 cows were randomly selected from the above data by way of preceding partial TD record, and then future milk yields were estimated using incomplete records from each cow randomly retained. Results suggested that we could predict the next four months milk yield with an error deviation of 4 kg. The correlation of more than 70% between predicted and observed values was estimated for the next four months milk yield. Even using only 3 TD records of some cows, the average milk yield of Korean Holstein cows would be predicted with high accuracy if compared with observed milk yield. Persistency of each cow was estimated which might be useful for selecting the cows with higher persistency. The results of the present study suggested the use of a $5^{th}$ order Legendre polynomial to predict the future milk yield of each cow.

• Journal of Animal Science and Technology
• /
• 제55권3호
• /
• pp.173-178
• /
• 2013

본 연구는 홀스타인 젖소, 436,690두의 검정일 유량기록 총 4,366,900개를 이용하여 비유지속성에 대한 특성과 새로운 평가형질로서의 가능성을 조사하는데 있다. 1산차, 2산차와 3산차 이상의 평균 비유지속성은 각각 97.5%, 95.1%와 94.6%였으며, 최고 유량 도달 이후 비유지속성이 일괄적으로 감소하는 추세를 나타내었다. 분만 후 최고유량에 도달하는 평균 비유일수는 약 50일로 조사 되었으나 실제로 2차 검정(36~66일)시에 최고 유량에 도달하는 개체의 기록은 전체 자료의 33.2%에 불과하였다. 또한 1차 검정시에 최고 유량에 도달한 개체들의 비유일수에 따른 유생산량 변화는 2~4차 검정에서 최고유량을 나타내는 개체들의 변화와는 많은 차이를 나타내었다. 평균 비유지속성에 대한 유전력과 반복력은 각각 0.16과 0.35로 추정되었으며, 10차 검정시 평균 비유지속성에 대한 검정차별 유전상관을 보면 7차 검정시 이상일 때 0.91이상이었으며, 검정차수가 줄어들수록 유전상관은 급격히 감소하였다. Data I에 대한 Data II와 III의 육종가 상관은 각각 0.80과 0.72, 순위 상관은 각각 0.78과 0.71로 나타났다. 결과적으로 자료가 추가될수록 육종가 및 순위 상관은 낮게 나타났다.

• 한국유기농업학회지
• /
• 제27권3호
• /
• pp.365-380
• /
• 2019

본 연구는 봄에 출생한 송아지 10두(3.90±0.26개월령)와 가을에 출생한 송아지 10두(4.10±0.30개월령)를 약 24개월간 조사료와 농후사료를 분리 급여하거나 또는 TMR을 급여하여 분만 후의 유생산과 비유지속성을 조사하였다. 처리구는 사료 급여 형태와 분만계절의 2가지 요인으로 육성기에 조사료와 농후사료를 분리하여 급여하고 봄에 분만한 CS구, 육성기에 조농분리 급여한 후 가을 분만한 CF구, 육성기에 TMR을 급여한 후 봄에 분만한 TS구 그리고 육성기에 TMR을 급여하고 가을에 분만한 TF구의 4가지로 구분하였다. 육성기의 건물섭취량은 분만계절의 영향을 받아 가을에 분만한 구가 봄에 분만한 구보다 높게 나타났으나(P<0.01), 사료급여 방법에 의해서는 유의한 차이를 나타내지 않았다. CP 섭취량과 TDN 섭취량은 분만계절(P<0.05)과 사료급여(P<0.01)에 의해 유의한 영향을 받았으며 가을에 분만한 구가 봄에 분만한 구에 비해 약 1.2% 높게 나타났고 TMR 급여구가 조농분리 급여구보다 약 4.7%정도 높은 결과를 보였다. 평균 산유량과 9, 10개월차의 산유량은 사료급여 방법에 의해 유의한 영향을 받아 TMR 급여구(TS구, TF구)가 조농분리 급여구(CS구, CF구) 보다 높은 결과를 나타내었다(평균 P<0.05; 9개월차와 10개월차 P<0.01). 평균 비유지속성은 분만계절(P<0.05)과 사료급여 방법(P<0.01)에 의해 유의한 영향을 받아 가을에 분만한 구가 봄에 분만한 구에 비해 높은 결과를 보였으며 TMR 급여구가 조농분리 급여구 보다 높은 결과를 나타냈다. 산유량의 결과와 유사하게 비유후기인 9, 10개월차에 사료급여에 의해 통계적 유의차를 보여(P<0.01) TMR 급여구가 약 8% 높았으며, 7개월차(P=0.12)와 8개월차(P=0.09)에도 높은 경향을 나타내었다. 따라서 육성기에 TMR을 급여하고 가을에 분만할 경우 초산우의 산유량과 비유지속성 증진에 효과적일 것으로 사료된다. 평균 유지율은 사료급여의 영향을 받아 TMR 급여구가 조농분리 급여구 보다 7.8% 높았는데(P<0.01) 육성기 TMR 급여가 분만 후 섭취행동에 영향을 주어 반추위의 안정화로 인해 유지율이 증가한 것으로 사료된다. 분만 후 3개월차에는 봄에 분만한 구가 가을에 분만한 구보다 유지방 함량이 낮았으며(P<0.05) 이는 계절적 차이에 의한 것으로 사료된다. MUN은 평균과 4, 5 및 6개월차에 조농분리 급여구에서 유의하게 높았다(4개월차 P<0.01; 5, 6개월차 P<0.05). 체세포수는 평균과 분만 후 3, 4개월차에 TMR 급여구가 조농분리 급여구 보다 높은 결과를 보였다(P<0.01). 결과를 종합해보면, 육성기에 TMR 급여방법을 적용하고 가을에 분만하는 경우 봄에 분만하는 경우에 비해 여름철 고온의 영향을 비교적 덜 받아 산유량과 비유지속성 뿐만 아니라 유지율 등이 개선되어 경제성이 향상되는 효과를 보았다. 그러나 본 실험은 봄과 가을의 분만계절이 미치는 영향만을 보았기 때문에 여름과 겨울의 분만계절의 영향에 대한 추가 실험이 필요할 것으로 사료된다.

• Journal of Animal Science and Technology
• /
• 제58권2호
• /
• pp.8.1-8.14
• /
• 2016

In this research data representing 72,946 primiparous cows from 724 herds with 638,063 total test day records calved between 2001 and 2011. These data were analysed to determine the effect of age at first and season of calving on parameters of the Wood lactation curve. Also, genetic trend of the lactation curve parameters in different calving years were evaluated. The results indicate that the highest rate of atypical lactation curve was related to cows that calved in summer (28.05 %). The maximum phenotypic relationship between initial milk yield and total 305-d milk yield was observed in cows calved in spring (0.40). The role of peak yield is more than peak time on 305-d total milk yield in primiparous Holstein. One month increase in age at first calving from 18 to 26 month raised 305-d milk yield by around 138 kg and from 27 to 32 month decreased by 61 kg. The persistency of lactation between 101 and 200 days is higher than that of 201-305 days. Our results indicate that the shape of lactation curve is largely dependent on the season of calving (higher level of milk production in cows which calved in autumn and winter). The heritabilities of parameters of lactation curve and persistency measures were low. The genetic trends for peak time, peak yield and 305-d milk yields were positive and estimated to be 0.019, 0.021 and 8.13 kg/year respectively. So the range from 24 to 26.5 month of calving is the optimum calving time in primiparous Holstein for maximizing 305-d milk yield.