Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
J Dairy Sci. 2018 May;101(5):4295-4306. doi: 10.3168/jds.2017-14089. Epub 2018 Feb 21.
The objective of this research was to estimate the genetic correlations between milk mid-infrared-predicted fatty acid groups and production traits in first-parity Canadian Holsteins. Contents of short-chain, medium-chain, long-chain, saturated, and unsaturated fatty acid groupings in milk samples can be predicted using mid-infrared spectral data for cows enrolled in milk recording programs. Predicted fatty acid group contents were obtained for 49,127 test-day milk samples from 10,029 first-parity Holstein cows in 810 herds. Milk yield, fat and protein yield, fat and protein percentage, fat-to-protein ratio, and somatic cell score were also available for these test days. Genetic parameters were estimated for the fatty acid groups and production traits using multiple-trait random regression test day models by Bayesian methods via Gibbs sampling. Three separate 8- or 9-trait analyses were performed, including the 5 fatty acid groups with different combinations of the production traits. Posterior standard deviations ranged from <0.001 to 0.01. Average daily genetic correlations were negative and similar to each other for the fatty acid groups with milk yield (-0.62 to -0.59) and with protein yield (-0.32 to -0.25). Weak and positive average daily genetic correlations were found between somatic cell score and the fatty acid groups (from 0.25 to 0.36). Stronger genetic correlations with fat yield, fat and protein percentage, and fat-to-protein ratio were found with medium-chain and saturated fatty acid groups compared with those with long-chain and unsaturated fatty acid groups. Genetic correlations were very strong between the fatty acid groups and fat percentage, ranging between 0.88 for unsaturated and 0.99 for saturated fatty acids. Daily genetic correlations from 5 to 305 d in milk with milk, protein yield and percentage, and somatic cell score traits showed similar patterns for all fatty acid groups. The daily genetic correlations with fat yield at the beginning of lactation were decreasing for long-chain and unsaturated fatty acid groups and increasing for short-chain fatty acids. Genetic correlations between fat percentage and fatty acids were increasing at the beginning of lactation for short- and medium-chain and saturated fatty acids, but slightly decreasing for long-chain and unsaturated fatty acid groups. These results can be used in defining fatty acid traits and breeding objectives.
本研究旨在估计加拿大荷斯坦奶牛初产牛泌乳中期近红外预测的脂肪酸组与生产性状间的遗传相关。利用牛只参加乳成分记录计划的近红外光谱数据，可以预测牛奶样本中短链、中链、长链、饱和和不饱和脂肪酸组的含量。从 810 个牛群的 10029 头初产荷斯坦奶牛中获得了 49127 个产奶日的预测脂肪酸组含量数据。这些产奶日还可获得产奶量、乳脂和乳蛋白产量、乳脂率和乳蛋白率、乳脂与乳蛋白比以及体细胞评分等数据。通过贝叶斯方法的 Gibbs 抽样，利用多性状随机回归产奶日模型对脂肪酸组和生产性状进行遗传参数估计。进行了 3 次单独的 8 或 9 性状分析，包括 5 个脂肪酸组与不同生产性状的组合。后验标准差范围为<0.001 至 0.01。脂肪酸组与产奶量（-0.62 至-0.59）和乳蛋白产量（-0.32 至-0.25）的平均日遗传相关为负且相似。体细胞评分与脂肪酸组间的平均日遗传相关为弱正（0.25 至 0.36）。与长链和不饱和脂肪酸组相比，中链和饱和脂肪酸组与乳脂产量、乳脂和乳蛋白率以及乳脂与乳蛋白比的遗传相关较强。脂肪酸组与乳脂率间的遗传相关很强，范围在不饱和脂肪酸组的 0.88 至饱和脂肪酸组的 0.99 之间。泌乳期 5 至 305 天的产奶量、乳蛋白产量和百分比及体细胞评分性状的日遗传相关在所有脂肪酸组中呈现相似的模式。长链和不饱和脂肪酸组的泌乳早期乳脂产量的日遗传相关呈下降趋势，短链脂肪酸的日遗传相关呈上升趋势。泌乳早期短链和中链及饱和脂肪酸的脂肪率与脂肪酸间的遗传相关呈上升趋势，长链和不饱和脂肪酸组的遗传相关则略有下降。这些结果可用于定义脂肪酸性状和制定选育目标。
