School of Veterinary Medicine, University of Rwanda-Nyagatare Campus, P.O. Box 57, Nyagatare, Rwanda.
Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, 75007, Uppsala, Sweden.
Trop Anim Health Prod. 2022 Feb 3;54(2):85. doi: 10.1007/s11250-022-03092-z.
Tropical regions are characterized by high temperature and humidity across the year. At high values of temperature humidity index (THI), there is a risk of heat stress leading to lower milk yield. The objective of this study was to describe the effect of season and the effect of maximum daily THI on milk yield of that day in purebred Ankole and Ankole-Friesian, Ankole-Jersey and Ankole-Sahiwal crosses in a tropical climate. In total, 53,730 records of daily milk yield from 183 cows in Rwanda were analyzed. The results showed that THI had a negative effect on daily milk yield above a threshold, but the effect was small (- 0.11 kg milk/THI unit at most). Purebred Ankole cows had the lowest daily milk yield and the lowest threshold (THI mean 66), as compared to the crossbreds (THI mean 68-69). Ankole-Friesian had a steeper decline in daily milk yield above the threshold than Ankole. The crossbreds, especially Ankole-Friesian, had higher daily milk yield than purebred Ankole also at very high THI. The results indicate some differences between breed groups in the way of coping with a hot and humid climate and raise questions about dairy cows' adaptation to such a climate.
热带地区全年高温高湿。在高温高湿度指数（THI）值较高的情况下，存在热应激风险，导致产奶量下降。本研究的目的是描述季节和最大日 THI 对热带气候下纯种安哥拉牛和安哥拉-弗里斯兰牛、安哥拉-泽西牛和安哥拉-萨希瓦尔牛杂交牛当天产奶量的影响。总共分析了卢旺达 183 头奶牛的 53730 份日产量记录。结果表明，THI 对每日产奶量有负面影响，但影响很小（最多为-0.11 公斤/THI 单位）。与杂交品种（THI 平均值为 68-69）相比，纯种安哥拉牛的日产量最低，阈值最低（THI 平均值为 66）。安哥拉-弗里斯兰牛的日产量在阈值以上的下降幅度比安哥拉牛陡峭。杂交品种，尤其是安哥拉-弗里斯兰牛，在 THI 非常高的情况下，日产量也高于纯种安哥拉牛。结果表明，不同品种群体在应对炎热潮湿气候方面存在一些差异，并提出了奶牛对这种气候的适应问题。
