Yamazaki T, Yamaguchi S, Takeda H, Osawa T, Hagiya K
Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Sapporo, 062-8555, Japan.
Hokkaido Dairy Milk Recording and Testing Association, Sapporo, 060-0004, Japan.
J Dairy Sci. 2020 Nov;103(11):10361-10373. doi: 10.3168/jds.2020-18494. Epub 2020 Aug 26.
The housing types (HST) in which dairy cows are kept and the feeding systems (FDS) used differ among farmers in Japan. Here, we investigated the genetic relationships among conception rate at first insemination (CR) and milk production traits (PROD) during the first 3 lactations of Holstein cows by using a multiple-trait model that considered the trait values of herds with different HST [tiestall (TSL) barn, freestall (FS) barn, or grazing (GZ)] and FDS as separate traits. Milk production and conception records of Holstein cows in the Hokkaido region of Japan (283,611 records for first lactation, 253,902 for second, and 181,197 for third) were analyzed. We categorized herds with TSL or FS into 2 types of FDS for cows: separate feeding (SF) of roughage plus concentrate or feeding of total mixed ration, in which roughage and concentrates were mixed before feeding. The PROD analyzed were cumulative milk, fat, and protein yields within 305 d and lactation persistency, which we defined as the difference between milk yields at 240 and 60 d in milk. We estimated the heritabilities for CR or PROD within each HST or HST × FDS group and the genetic correlations between these traits within each group or across different groups within each lactation by using a 3-HST (TSL, FS, and GZ) × 2-trait (CR and each PROD) or 2-HST (TSL and FS) × 2-FDS × 2-trait animal model. Heritability estimates for CR in GZ were higher than those in TSL or FS, and genetic correlations for CR between GZ and TSL or FS barns were weaker than those between TSL and FS barns. In addition, genetic correlations between CR and PROD in GZ were weaker than those in TSL and FS barns. In the comparison among the 4 HST × FDS except GZ, heritability estimates for CR in FS × SF were higher than those in the others, and genetic correlations for CR between FS × SF and the other systems were relatively weak. These results indicated that differences in the production system for Holstein cows influence genotypic effects in terms of the cows' ability to conceive and the genetic relationships between fertility traits and milk production traits.
在日本，奶农饲养奶牛的畜舍类型（HST）和使用的饲养系统（FDS）各不相同。在此，我们通过使用多性状模型，研究了荷斯坦奶牛首次输精时的受胎率（CR）与前3个泌乳期的产奶性状（PROD）之间的遗传关系，该模型将具有不同畜舍类型[栓系牛舍（TSL）、散栏牛舍（FS）或放牧（GZ）]和饲养系统的牛群的性状值视为独立性状。分析了日本北海道地区荷斯坦奶牛的产奶和受胎记录（第1泌乳期283,611条记录，第2泌乳期253,902条，第3泌乳期181,197条）。我们将采用栓系或散栏饲养的牛群的饲养系统分为2种类型：粗饲料加精饲料的分开饲喂（SF）或全混合日粮饲喂，即粗饲料和精饲料在饲喂前混合。分析的产奶性状包括305天内的累计产奶量、脂肪产量和蛋白质产量以及泌乳持续力，我们将泌乳持续力定义为产奶240天和60天时产奶量的差值。我们使用3种畜舍类型（TSL、FS和GZ）×2个性状（CR和各产奶性状）或2种畜舍类型（TSL和FS）×2种饲养系统×2个性状的动物模型，估计了每个畜舍类型或畜舍类型×饲养系统组内CR或产奶性状的遗传力，以及每个泌乳期内每组或不同组之间这些性状的遗传相关性。放牧饲养的奶牛CR的遗传力估计值高于栓系或散栏饲养的奶牛，放牧与栓系或散栏牛舍之间CR的遗传相关性弱于栓系和散栏牛舍之间的相关性。此外，放牧饲养的奶牛CR与产奶性状之间的遗传相关性弱于栓系和散栏牛舍的奶牛。在除放牧外的4种畜舍类型×饲养系统的比较中，散栏×分开饲喂组中CR的遗传力估计值高于其他组，散栏×分开饲喂组与其他系统之间CR的遗传相关性相对较弱。这些结果表明，荷斯坦奶牛生产系统的差异在奶牛受孕能力以及繁殖性状与产奶性状之间的遗传关系方面影响基因型效应。
