Boonkum Wuttigrai, Teawyoneyong Watcharapong, Chankitisakul Vibuntita, Duangjinda Monchai, Buaban Sayan
Department of Animal Science, Faculty of Agriculture, Khon Kean University, Khon Kean 40002, Thailand.
Network Center for Animal Breeding and Omics Research, Khon Kaen University, Khon Kaen 40002, Thailand.
Animals (Basel). 2024 Oct 19;14(20):3026. doi: 10.3390/ani14203026.
Heat stress severely affects dairy cattle production and reproduction performances in tropical regions. Genetic selection to maintain adequate yield and reproductive performance while enhancing their ability to withstand heat is essential for improving the genetics of dairy cows. Therefore, in this study, we aimed to estimate genetic parameters affecting production and reproduction performances under heat stress conditions in dairy cattle and to investigate the threshold point of heat stress for milk yield (MY), milk fat-to-protein ratio (FPR), and conception rate (CR) in Thai-Holstein dairy cattle. The data included 168,124 records related to MY and milk FPR and 21,278 records of CR in Thai-Holstein dairy cattle, covering the period from 1990 to 2007. A multiple-trait threshold-linear random regression model based on a Bayesian approach via Gibbs sampling was used to estimate variance components, genetic parameters (heritability values, and genetic correlations), and decline rates for each studied trait. The threshold point of heat stress was identified as a temperature and humidity index (THI) of 76. At THI76, a decline was observed in the MY, milk FPR, and CR of Thai dairy cattle. The heritability estimates for MY, milk FPR and CR were 0.347 ± 0.032, 0.293 ± 0.021, and 0.032 ± 0.001, respectively. The genetic correlation between MY and milk FPR and MY and CR were -0.24 and -0.53, respectively, whereas those between milk FPR and heat tolerance as well as between CR and heat tolerance were -0.48 and -0.49, respectively. In addition, the decline rates in MY, milk FPR, and CR were found to be associated with a high percentage of Holstein genetics. In conclusion, the results obtained in this study reveal that the simultaneous consideration of the MY, milk FPR, CR, and heat tolerance traits of Thai-Holstein dairy cattle is possible. In addition, developing a genetic model that incorporates THI is essential for sustainably addressing heat stress problems.
热应激严重影响热带地区奶牛的生产和繁殖性能。在提高奶牛耐热能力的同时，通过遗传选择来维持足够的产量和繁殖性能，对于改善奶牛的遗传特性至关重要。因此，在本研究中，我们旨在估计影响奶牛热应激条件下生产和繁殖性能的遗传参数，并研究泰国荷斯坦奶牛产奶量（MY）、乳脂蛋白比（FPR）和受胎率（CR）的热应激阈值点。数据包括1990年至2007年期间泰国荷斯坦奶牛与MY和乳FPR相关的168,124条记录以及21,278条CR记录。基于贝叶斯方法通过吉布斯采样的多性状阈值线性随机回归模型用于估计方差分量、遗传参数（遗传力值和遗传相关性）以及每个研究性状的下降率。热应激阈值点确定为温度湿度指数（THI）76。在THI76时，观察到泰国奶牛的MY、乳FPR和CR下降。MY、乳FPR和CR的遗传力估计值分别为0.347±0.032、0.293±0.021和0.032±0.001。MY与乳FPR以及MY与CR之间的遗传相关性分别为-0.24和-0.53，而乳FPR与耐热性之间以及CR与耐热性之间的遗传相关性分别为-0.48和-0.49。此外，发现MY、乳FPR和CR的下降率与高比例的荷斯坦遗传有关。总之，本研究获得的结果表明，可以同时考虑泰国荷斯坦奶牛的MY、乳FPR、CR和耐热性性状。此外，开发纳入THI的遗传模型对于可持续解决热应激问题至关重要。
