Zhang Bihong, Wen Yongqiang, Zhang Zixin, Liu Qimin, Wang Yazhou, Zhao Chenxu, Wang Jianguo
College of Veterinary Medicine, Northwest A&F University, Yangling, China.
Front Vet Sci. 2025 Sep 1;12:1651670. doi: 10.3389/fvets.2025.1651670. eCollection 2025.
Global warming increases the risk of heat stress in dairy cattle, thereby jeopardizing their health and the economic benefits of dairy farms. Chromium propionate (CrPro) is a chromium source permitted for use in feed additives. However, research on the effects of CrPro on heat-stressed dairy cows is limited. Therefore, this study assessed the effects of different doses of CrPro on heat-stressed dairy cows. Holstein dairy cows with similar body condition, milk yield, and parity were randomly divided into three groups: the control group (Con), the low-dose group (CrL), and the high-dose group (CrH), with 10 cows per group. CrPro was supplemented at doses of 0, 4, and 8 mg/(d·cow) in the basal diets of each group, respectively. The trial lasted for 45 days. The temperature-humidity index (THI) in the cowshed was monitored daily to assess the heat stress status of the cows. Daily milk yield was recorded, and rectal temperature was measured according to experimental requirements. Milk composition, antioxidant capacity, liver enzyme activity, lipid metabolism, and other parameters were analyzed. The composition and diversity of the rumen microbiota were also assessed. Results showed that the average THI in the cowshed during the trial period (0-45 days) was 74.97 ± 2.85, indicating that dairy cows used in this study experienced mild heat stress. Compared with the Con group, the CrL and CrH groups had reduced rectal temperature and respiratory rate. The CrH group had significantly lower milk yield loss and somatic cell count ( < 0.05). No significant differences were observed in milk composition, antioxidant capacity, liver enzyme activity, or lipid metabolism between the CrL and CrH groups ( > 0.05). Compared with the CrH group, the CrL group had lower volatile fatty acids (VFAs) (acetate, propionate, butyrate, isobutyrate, valerate, and isovalerate) in rumen fluid. Compared with the control group, both CrL and CrH groups exhibited enhanced microbial abundance and an optimized ruminal community structure. Overall, an 8 mg/(d·cow) dose of CrPro had a greater impact on improving production performance and economic benefits. The findings of this study provide data support for selecting an appropriate CrPro dosage to reduce heat stress-induced economic losses on dairy farms.
全球变暖增加了奶牛热应激的风险，从而危及它们的健康以及奶牛场的经济效益。丙酸铬（CrPro）是一种允许用于饲料添加剂的铬源。然而，关于丙酸铬对热应激奶牛影响的研究有限。因此，本研究评估了不同剂量的丙酸铬对热应激奶牛的影响。将体况、产奶量和胎次相似的荷斯坦奶牛随机分为三组：对照组（Con）、低剂量组（CrL）和高剂量组（CrH），每组10头奶牛。分别在每组基础日粮中按0、4和8毫克/（天·头）的剂量添加丙酸铬。试验持续45天。每天监测牛舍内的温度湿度指数（THI），以评估奶牛的热应激状态。记录每日产奶量，并根据实验要求测量直肠温度。分析牛奶成分、抗氧化能力、肝酶活性、脂质代谢等参数。还评估了瘤胃微生物群的组成和多样性。结果表明，试验期（0 - 45天）牛舍内的平均THI为74.97±2.85，表明本研究中使用的奶牛经历了轻度热应激。与Con组相比，CrL组和CrH组的直肠温度和呼吸频率降低。CrH组的产奶量损失和体细胞计数显著更低（<0.05）。CrL组和CrH组在牛奶成分、抗氧化能力、肝酶活性或脂质代谢方面未观察到显著差异（>0.05）。与CrH组相比，CrL组瘤胃液中的挥发性脂肪酸（VFAs，乙酸、丙酸、丁酸、异丁酸、戊酸和异戊酸）含量更低。与对照组相比，CrL组和CrH组的微生物丰度均有所提高，瘤胃群落结构得到优化。总体而言，8毫克/（天·头）剂量的丙酸铬对提高生产性能和经济效益有更大影响。本研究结果为选择合适的丙酸铬剂量以减少奶牛场热应激导致的经济损失提供了数据支持。
