Bobbo Tania, Penasa Mauro, Cassandro Martino
Department of Agronomy, Food, Natural resources, Animals and Environment (DAFNAE), University of Padova, Viale dell'Università 16, 35020 Legnaro, Italy.
Animals (Basel). 2020 Dec 16;10(12):2406. doi: 10.3390/ani10122406.
The growing interest of consumers for milk and dairy products of high nutritional value has pushed researchers to evaluate the feasibility of including fatty acids (FA) in selection programs to modify milk fat profile and improve its nutritional quality. Therefore, the aim of this study was to estimate genetic parameters of FA profile predicted by mid-infrared spectroscopy, milk yield, composition, and total and differential somatic cell count. Edited data included 35,331 test-day records of 25,407 Italian Holstein cows from 652 herds. Variance components and heritability were estimated using single-trait repeatability animal models, whereas bivariate repeatability animal models were used to estimate genetic and phenotypic correlations between traits, including the fixed effects of stage of lactation, parity, and herd-test-date, and the random effects of additive genetic animal, cow permanent environment and the residual. Heritabilities and genetic correlations obtained in the present study reflected both the origins of FA (extracted from the blood or synthesized de novo by the mammary gland) and their grouping according to saturation or chain length. In addition, correlations among FA groups were in line with correlation among individual FA. Moderate negative genetic correlations between FA and milk yield and moderate to strong positive correlations with fat, protein, and casein percentages suggest that actual selection programs are currently affecting all FA groups, not only the desired ones (e.g., polyunsaturated FA). The absence of association with differential somatic cell count and the weak association with somatic cell score indicate that selection on FA profile would not affect selection on resistance to mastitis and vice versa. In conclusion, our findings suggest that genetic selection on FA content is feasible, as FA are variable and moderately heritable. Nevertheless, in the light of correlations with other milk traits estimated in this study, a clear breeding goal should first be established.
消费者对高营养价值的牛奶和乳制品兴趣日增，这促使研究人员评估在选育计划中纳入脂肪酸（FA）以改变乳脂肪组成并提高其营养品质的可行性。因此，本研究的目的是估计通过中红外光谱预测的FA组成、产奶量、乳成分以及总体细胞数和不同体细胞数的遗传参数。编辑后的数据包括来自652个牛群的25,407头意大利荷斯坦奶牛的35,331条测定日记录。使用单性状重复性动物模型估计方差组分和遗传力，而双变量重复性动物模型用于估计性状之间的遗传和表型相关性，包括泌乳阶段、胎次和牛群-测定日期的固定效应，以及加性遗传动物、奶牛永久环境和残差的随机效应。本研究中获得的遗传力和遗传相关性既反映了FA的来源（从血液中提取或由乳腺重新合成），也反映了它们根据饱和度或链长的分组情况。此外，FA组之间的相关性与单个FA之间的相关性一致。FA与产奶量之间存在中等程度的负遗传相关性，与乳脂肪、乳蛋白和酪蛋白百分比之间存在中等至强的正相关性，这表明目前的实际选育计划正在影响所有FA组，而不仅仅是期望的FA组（例如，多不饱和FA）。与不同体细胞数无关联以及与体细胞评分的关联较弱，这表明对FA组成的选择不会影响对乳腺炎抗性的选择，反之亦然。总之，我们的研究结果表明，对FA含量进行遗传选择是可行的，因为FA具有变异性且具有中等遗传力。然而，鉴于本研究中估计的与其他乳性状的相关性，首先应确立明确的育种目标。
