Menéndez-Buxadera Alberto, Muñoz-Mejías Eva, Sánchez Manuel, Serradilla Juan Manuel, Molina Antonio
Meragem Group, Department of Genetic, Campus de Rabanales, University of Córdoba, Ctra, Madrid-Cádiz, km 396, 14014 Córdoba, Spain.
Department of Animal Pathology, Animal Production, Food Science and Food Technology, University of Las Palmas de Gran Canaria, 35413 Las Palmas, Spain.
Animals (Basel). 2021 Mar 8;11(3):736. doi: 10.3390/ani11030736.
We studied the effect of the Temperature Humidity Index (THI) (i.e., the average of temperature and relative humidity registered at meteorological stations) closest to the farms taken during the test day (TD), for total daily protein and fat yields (fpy) of the three main Spanish dairy goats. The data were from Florida (11,244 animals and 126,825 TD), Malagueña (12,215 animals and 141,856 TD) and Murciano Granadina (5162 animals and 62,834 TD) breeding programs and were studied by different linear models to estimate the nature of the fpy response throughout the THI and the weeks of lactation (Days in Milk, DIM) trajectories. The results showed an antagonism between THI and DIM, with a marked depression in the fpy level in animals kept in the hot zone of the THI values (THI > 25) compared with those in the cold zone (THI ≤ 16), with a negative impact equivalent to production of 13 to 30 days. We used a Reaction Norm model (RN), including THI and DIM as fixed covariates and a Test Day Model (TDM), to estimate the genetic (co)variance components. The heritability and genetic correlations estimated with RN and TDM showed a decreased pattern along the scale of THI and DIM, with slight differences between breeds, meaning that there was significant genetic variability in the animal's ability to react to different levels of THI, which is not constant throughout the DIM, showing the existence of genotype-environment interaction. The breeding values (BV) of all animals for each level of THI and DIM were subject to a principal component analysis, and the results showed that 89 to 98% of the variance between the BV was explained by the two first eigenvalues. The standardized BV were weighted with the corresponding eigenvector coefficients to construct an index that showed, in a single indicator, the most complete expression of the existing genetic variability in the animals' ability to produce fpy along the trajectories of THI and DIM. This new option will make it easier to select animals which are more productive, and with better adaptability to heat stress, as well as enabling us to exploit genetic variations in the form of the response to heat stress to be adapted to different production systems.
我们研究了测试日（TD）期间距离养殖场最近的温度湿度指数（THI）（即气象站记录的温度和相对湿度的平均值）对西班牙三种主要奶山羊每日总蛋白质和脂肪产量（fpy）的影响。数据来自佛罗里达（11244只动物和126825个测试日）、马拉盖纳（12215只动物和141856个测试日）和穆尔西亚诺格拉纳迪纳（5162只动物和62834个测试日）的育种项目，并通过不同的线性模型进行研究，以估计整个THI和泌乳周数（产奶天数，DIM）轨迹上fpy反应的性质。结果表明，THI和DIM之间存在拮抗作用，与处于THI值低温区（THI≤16）的动物相比，处于THI值高温区（THI>25）的动物fpy水平明显下降，负面影响相当于13至30天的产量。我们使用了一个反应规范模型（RN），将THI和DIM作为固定协变量，以及一个测试日模型（TDM），来估计遗传（协）方差分量。用RN和TDM估计的遗传力和遗传相关性在THI和DIM范围内呈下降趋势，不同品种之间略有差异，这意味着动物对不同水平THI的反应能力存在显著的遗传变异性，且在整个DIM期间并非恒定不变，表明存在基因型 - 环境相互作用。对所有动物在每个THI和DIM水平下的育种值（BV）进行主成分分析，结果表明，BV之间89%至98%的方差由前两个特征值解释。标准化的BV用相应的特征向量系数加权，以构建一个指数，该指数在单一指标中显示了动物在THI和DIM轨迹上产生fpy的能力中现有遗传变异性的最完整表达。这个新方法将使选择更高产、对热应激适应性更强的动物变得更容易，同时使我们能够利用对热应激反应形式的遗传变异来适应不同的生产系统。
