Osei-Amponsah Richard, Dunshea Frank R, Leury Brian J, Abhijith Archana, Chauhan Surinder S
School of Agriculture, Food and Ecosystem Sciences, Faculty of Science, The University of Melbourne, Melbourne 3010, Australia.
Department of Animal Science, School of Agriculture, College of Basic and Applied Sciences, University of Ghana, Legon, Accra P.O. Box LG 226, Ghana.
Animals (Basel). 2023 Jul 10;13(14):2259. doi: 10.3390/ani13142259.
Dairy cattle predicted by genomic breeding values to be heat tolerant are known to have less milk production decline and lower core body temperature increases in response to elevated temperatures. In a study conducted at the University of Melbourne's Dookie Robotic Dairy Farm during summer, we identified the 20 most heat-susceptible and heat-tolerant cows in a herd of 150 Holstein Friesian lactating cows based on their phenotypic responses (changes in respiration rate, surface body temperature, panting score, and milk production). Hair samples were collected from the tip of the cows' tails following standard genotyping protocols. The results indicated variation in feed saved and HT genomic estimated breeding values (GEBVs) ( ≤ 0.05) across age, indicating a potential for their selection. As expected, the thermotolerant group had higher GEBVs for HT and feed saved but lower values for milk production. In general, younger cows had superior GEBVs for the Balanced Performance Index (BPI) and Australian Selection Index (ASI), whilst older cows were superior in fertility, feed saved (FS), and HT. This study demonstrated highly significant ( ≤ 0.001) negative correlations (-0.28 to -0.74) between HT and GEBVs for current Australian dairy cattle selection indices (BPI, ASI, HWI) and significant ( ≤ 0.05) positive correlations between HT and GEBVs for traits like FS (0.45) and fertility (0.25). Genomic selection for HT will help improve cow efficiency and sustainability of dairy production under hot summer conditions. However, a more extensive study involving more lactating cows across multiple farms is recommended to confirm the associations between the phenotypic predictors of HT and GEBVs.
根据基因组育种值预测为耐热的奶牛，已知在温度升高时产奶量下降较少，核心体温升高较低。在墨尔本大学杜基机器人奶牛场夏季进行的一项研究中，我们根据150头荷斯坦弗里生泌乳奶牛的表型反应（呼吸频率、体表温度、喘气评分和产奶量变化），确定了其中最易受热应激和最耐热的20头奶牛。按照标准基因分型方案从奶牛尾巴尖端采集毛发样本。结果表明，不同年龄的奶牛在节省饲料量和耐热性基因组估计育种值（GEBVs）方面存在差异（≤0.05），这表明它们具有选择潜力。正如预期的那样，耐热组的耐热性和节省饲料量的GEBVs较高，但产奶量的GEBVs较低。总体而言，年轻奶牛在平衡性能指数（BPI）和澳大利亚选择指数（ASI）方面具有较好的GEBVs，而年长奶牛在繁殖力、节省饲料量（FS）和耐热性方面表现更优。这项研究表明，对于当前澳大利亚奶牛选择指数（BPI、ASI、HWI），耐热性与GEBVs之间存在高度显著（≤0.001）的负相关（-0.28至-0.74），而对于FS（0.45）和繁殖力（0.25）等性状，耐热性与GEBVs之间存在显著（≤0.05）的正相关。在炎热的夏季条件下，对耐热性进行基因组选择将有助于提高奶牛的效率和奶牛生产的可持续性。然而，建议进行更广泛的研究，涉及多个农场的更多泌乳奶牛，以确认耐热性的表型预测指标与GEBVs之间的关联。
