Relationships between conception rate in Holstein heifers and cows and milk yield at various stages of lactation.
Relationships between conception rate in Holstein heifers and cows and milk yield at various stages of lactation.
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荷斯坦小母牛和奶牛受胎率与泌乳各阶段产奶量的关系。
DOI：
10.1017/s1751731113000633
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Suzuki
中科院分区：
文献类型：
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作者：
K. Hagiya;Y. Terawaki;T. Yamazaki;Y. Nagamine;F. Itoh;S. Yamaguchi;H. Abe;Y. Gotoh;T. Kawahara;Y. Masuda;M. Suzuki
我们研究了日本荷斯坦小母牛（即尚未产下第一头小牛的动物）和奶牛首次服务时的受孕率（CR）与其试验日（TD）产奶量之间的关系。数据包括2000年至2008年期间首次产犊的小母牛和奶牛的人工授精（AI）记录，以及第一次至第三次泌乳期间6至305天的TD产奶量（DIM）。CR被定义为一个二元特征，第一个AI是失败或成功。应用阈值线性动物模型估计不同泌乳阶段小母牛或母牛的CR与TD产奶量之间的遗传相关。采用Gibbs抽样的贝叶斯方法，对产奶量CR和TD的每一个组合进行了双性状遗传分析。CR遗传力的后验均值为：小母牛0.031，初泌乳牛0.034，二泌乳牛0.028。TD产奶量的遗传力随着DIM的增加而增加，从0.324增加到0.433，但在第一泌乳期210 DIM后略有下降。这些遗传力从第二次和第三次泌乳较高，在后期阶段的哺乳期比在早期阶段。小母牛CR与总TD产量之间的遗传相关的后验均值为正（0.082 ~ 0.287），而奶牛CR与第一、第二泌乳期产奶量之间的遗传相关均为负（-0.121 ~-0.250）。因此，在泌乳的每一个阶段，选择的方向增加产奶量可能会降低CR奶牛。泌乳曲线形状与产奶量之间的遗传相关性很弱，因为泌乳期产奶量与产奶量之间的遗传相关性是恒定的。
We investigated the relationships between conception rates (CRs) at first service in Japanese Holstein heifers (i.e. animals that had not yet had their first calf) and cows and their test-day (TD) milk yields. Data included records of artificial insemination (AI) for heifers and cows that had calved for the first time between 2000 and 2008 and their TD milk yields at 6 through 305 days in milk (DIM) from first through third lactations. CR was defined as a binary trait for which first AI was a failure or success. A threshold-linear animal model was applied to estimate genetic correlations between CRs of heifers or cows and TD milk yield at various lactation stages. Two-trait genetic analyses were performed for every combination of CR and TD milk yield by using the Bayesian method with Gibbs sampling. The posterior means of the heritabilities of CR were 0.031 for heifers, 0.034 for first-lactation cows and 0.028 for second-lactation cows. Heritabilities for TD milk yield increased from 0.324 to 0.433 with increasing DIM but decreased slightly after 210 DIM during first lactation. These heritabilities from the second and third lactations were higher during late stages of lactation than during early stages. Posterior means of the genetic correlations between heifer CR and all TD yields were positive (range, 0.082 to 0.287), but those between CR of cows and milk yields during first or second lactation were negative (range, -0.121 to -0.250). Therefore, during every stage of lactation, selection in the direction of increasing milk yield may reduce CR in cows. The genetic relationships between CR and lactation curve shape were quite weak, because the genetic correlations between CR and TD milk yield were constant during the lactation period.