University of Liège, Gembloux Agro-Bio Tech, Animal Science Unit, B-5030 Gembloux, Belgium.
J Dairy Sci. 2010 May;93(5):2215-28. doi: 10.3168/jds.2009-2720.
The objective of this study was to investigate the genetic relationship between body condition score (BCS) and reproduction traits for first-parity Canadian Ayrshire and Holstein cows. Body condition scores were collected by field staff several times over the lactation in herds from Québec, and reproduction records (including both fertility and calving traits) were extracted from the official database used for the Canadian genetic evaluation of those herds. For each breed, six 2-trait animal models were run; they included random regressions that allowed the estimation of genetic correlations between BCS over the lactation and reproduction traits that are measured as a single lactation record. Analyses were undertaken on data from 108 Ayrshire herds and 342 Holstein herds. Average daily heritabilities of BCS were close to 0.13 for both breeds; these relatively low estimates might be explained by the high variability among herds and BCS evaluators. Genetic correlations between BCS and interval fertility traits (days from calving to first service, days from first service to conception, and days open) were negative and ranged between -0.77 and -0.58 for Ayrshire and between -0.31 and -0.03 for Holstein. Genetic correlations between BCS and 56-d nonreturn rate at first insemination were positive and moderate. The trends of these genetic correlations over the lactation suggest that a genetically low BCS in early lactation would increase the number of days that the primiparous cow was not pregnant and would decrease the chances of the primiparous cow to conceive at first service. Genetic correlations between BCS and calving traits were generally the strongest at calving and decreased with increasing days in milk. The correlation between BCS at calving and maternal calving ease was 0.21 for Holstein and 0.31 for Ayrshire and emphasized the relationship between fat cows around calving and dystocia. Genetic correlations between calving traits and BCS during the subsequent lactation were moderate and favorable, indicating that primiparous cows with a genetically high BCS over the lactation would have a greater chance of producing a calf that survived (maternal calf survival) and would transmit the genes that allowed the calf to be born more easily (maternal calving ease) and to survive (direct calving ease).
本研究旨在探讨加拿大首产 Ayrshire 和荷斯坦奶牛的体况评分（BCS）与繁殖性状之间的遗传关系。体况评分由现场工作人员在魁北克的牧场多次采集，繁殖记录（包括生育力和产犊性状）从用于这些牧场加拿大遗传评估的官方数据库中提取。对于每个品种，运行了六个 2 性状动物模型；它们包括允许在哺乳期内估计 BCS 与繁殖性状之间遗传相关性的随机回归，这些性状被测量为单个哺乳期记录。对来自 108 个 Ayrshire 牧场和 342 个 Holstein 牧场的数据进行了分析。两种品种的 BCS 平均日遗传力均接近 0.13；这些相对较低的估计可能是由于牧场和 BCS 评估者之间的高度变异性所致。BCS 与间隔生育力性状（从配种到首次配种、从首次配种到受胎和空怀天数）之间的遗传相关性为负，范围为 -0.77 至 -0.58 对于 Ayrshire，-0.31 至 -0.03 对于 Holstein。BCS 与首次配种 56 天的非返情率之间的遗传相关性为正且中等。这些遗传相关性在哺乳期的趋势表明，哺乳期早期的低 BCS 会增加初产奶牛未怀孕的天数，并降低初产奶牛首次配种受孕的机会。BCS 与产犊性状之间的遗传相关性通常在产犊时最强，随着泌乳天数的增加而降低。荷斯坦牛的产犊时 BCS 与母体产犊易感性的相关性为 0.21，Ayrshire 的相关性为 0.31，这强调了产犊前后奶牛的脂肪与难产之间的关系。哺乳期后产犊性状与 BCS 之间的遗传相关性为中等且有利，表明哺乳期 BCS 较高的初产奶牛更有可能产下存活的小牛（母犊存活率），并传递使小牛更容易出生（母犊易产）和存活（直接产犊易）的基因。
