【摘要】 为研究日粮中添加不同水平丙酸铬(CrPro)对缓解奶牛热应激的作用，本试验将体况、产奶量、胎次相近的荷斯坦奶牛随机分为对照组(Con)、低剂量组(CrL)和高剂量组(CrH),每组10头，分别按照0、4和8 mg/(d·头)剂量在泌乳期奶牛基础日粮中添加CrPro,试验期为45 d,每天检测牛舍温湿度指数(THI)用以评估奶牛的热应激状态，每天记录奶牛产奶量，自0 d开始每15 d固定时间记录直肠温度和呼吸频率，并采集乳样和血样，用以分析乳成分、抗氧化能力、肝酶活性、脂代谢、糖代谢、氮代谢和血液电解质指标。结果显示，试验期间(0～45 d)牛舍THI的平均值为74.97±2.85;与Con组相比，CrH组产奶量损失和乳体细胞数显著降低(P<0.05),CrL组和CrH组乳成分、抗氧化能力、肝酶活性、脂代谢、糖代谢、氮代谢和血液电解质指标均无显著差异(P>0.05)。结果表明，整个试验期间，各组奶牛均受到轻度热应激刺激(THI>72),在泌乳期奶牛基础日粮中添加8 mg/(d·头) CrPro可以提高热应激奶牛产奶量，降低乳体细胞数以提高乳品质，且该试验剂量对热应激奶牛乳成分、抗氧化能力、肝酶活性、脂代谢、糖代谢、氮代谢和血液电解质指标无显著影响。更多还原

【Abstract】 To investigate the effects of different levels of chromium propionate(CrPro) supplementation in the diet on alleviating heat stress in dairy cows, this study randomly divided Holstein dairy cows with similar body condition, milk production, and parity into three groups: control group(Con), low-dose group(CrL), and high-dose group(CrH), with 10 cows in each group. CrPro was added to the basal diet of lactating cows at doses of 0, 4, and 8 mg/(d·head) in the Con, CrL, and CrH groups, respectively. The experiment lasted for 45 days. The temperature humidity index(THI) of the barns was measured daily to assess the heat stress status of the cows. Milk production was recorded daily, and rectal temperature and respiratory rate were measured at fixed intervals of 15 days starting from day 0. Milk and blood samples were collected to analyze milk composition, antioxidant capacity, hepatic enzyme activity, lipid metabolism, glucose metabolism, nitrogen metabolism, and blood electrolyte indexes. The results showed that the average THI in the barns during the experimental period(0-45 days) was 74.97±2.85. Compared to the Con group, the milk production loss and milk somatic cell count in CrH group reduced significantly(P<0.05). There were no significant differences in milk composition, antioxidant capacity, hepatic enzyme activity, lipid metabolism, glucose metabolism, nitrogen metabolism, and blood electrolyte indexes between the CrL and CrH groups(P>0.05). These results indicate that all groups of cows experienced mild heat stress stimulation(THI>72) throughout the experimental period. Adding 8 mg/(d·head) of CrPro to the basal diet of lactating cows can increase milk production and reduce milk somatic cell count to improve milk quality in heat-stressed cows. Furthermore, this dosage of CrPro had no significant impact on milk composition, antioxidant capacity, hepatic enzyme activity, lipid metabolism, glucose metabolism, nitrogen metabolism, and blood electrolyte indexes in heat-stressed cows.更多还原