Department of Animal Science, School of Agriculture, Shiraz University, Shiraz 71441-65186, Iran.
Department of Animal Science, College of Agriculture, Shahrekord University, Shahrekord 34141-88186, Iran.
J Dairy Sci. 2018 Nov;101(11):9876-9887. doi: 10.3168/jds.2017-14154. Epub 2018 Aug 29.
We investigated the effect of Cr supplementation on growth performance, feeding behavior, health status, and blood metabolites of summer-exposed dairy calves during the pre- and postweaning periods. A total of 24 newborn Holstein female calves (1 d of age; 42.1 ± 0.89 kg of body weight) were assigned randomly to a control group (no Cr supplement; Cr-) or a Cr group (Cr+) receiving 0.05 mg of Cr/kg of body weight. During the study period, the average maximum temperature-humidity index was 81.3 units, indicating a high environmental heat load. Chromium was provided in colostrum and milk during the preweaning period, and in the starter feed during the postweaning period. Calves had free access to fresh water and starter feed throughout the experiment and were weaned on d 63. Starter feed intake and total dry matter intake were greater in Cr+ calves. Despite decreased meal frequency in Cr+ calves, during the preweaning period the starter feed intake increased due to increases in meal duration and meal size and a tendency for greater meal interval. Increased postweaning starter intake in Cr+ calves was attributed to a tendency for an increase in meal duration. Chromium-supplemented calves had greater overall weight gain, but their feed efficiency and rectal temperature were not affected by Cr treatment. Chromium supplementation tended to increase the heart girth during the preweaning and overall periods and increased the hip width during the postweaning and overall periods. Respiration rates were lower in Cr+ calves than Cr- calves during the preweaning and overall periods. During the preweaning period, the time spent in eating and ruminating per 12-h period was not affected by Cr treatment. During the postweaning period, the rumination time (min per 12-h period) was unaffected but total eating time (min per 12-h period) increased in Cr+ calves. Times spent resting, drinking, standing, lying, and in nonnutritive oral behaviors were not affected by treatments during the pre- and postweaning periods. Chromium supplementation had no effects on serum concentrations of cortisol, triiodothyronine, and thyroxine measured at weaning or the end of the trial. The Cr+ calves tended to have higher serum concentrations of glucose and a higher ratio of insulin to glucose measured at the end of the trial. In conclusion, Cr supplementation of both liquid and solid feeds improved growth performance in summer-exposed calves as a result of reduced respiration rate and increased feed intake; however, no beneficial effects were found on feed efficiency and insulin metabolism.
我们研究了铬补充剂对夏季暴露的奶牛犊牛在断奶前后的生长性能、采食行为、健康状况和血液代谢物的影响。共有 24 头新生荷斯坦雌性犊牛(1 日龄;体重 42.1±0.89kg)随机分为对照组(无铬补充;Cr-)或 Cr 组(Cr+),接受 0.05mg/kg 体重的铬。在研究期间,平均最高温湿度指数为 81.3 单位,表明环境热负荷较高。铬在哺乳期通过初乳和牛奶提供,在断奶后通过开食料提供。犊牛在整个实验过程中可自由饮用新鲜水和开食料,并于第 63 天断奶。Cr+犊牛的开食料采食量和总干物质采食量较大。尽管 Cr+犊牛的采食频率降低,但在哺乳期,由于采食持续时间、采食大小和采食间隔增加,开食料采食量增加。Cr+犊牛断奶后开食料采食量增加归因于采食持续时间增加的趋势。补充铬的犊牛整体增重较大,但铬处理对其饲料效率和直肠温度没有影响。铬补充剂在哺乳期和整个哺乳期有增加胸围的趋势,在断奶后和整个哺乳期有增加髋宽的趋势。与 Cr-犊牛相比,Cr+犊牛在哺乳期和整个哺乳期的呼吸率较低。在哺乳期,每 12 小时的采食和反刍时间不受 Cr 处理的影响。在断奶后,反刍时间(每 12 小时 min)不受影响,但 Cr+犊牛的总采食时间(每 12 小时 min)增加。在断奶前后,休息、饮水、站立、躺卧和非营养性口腔行为时间不受处理的影响。铬补充剂对断奶时和试验结束时血清皮质醇、三碘甲状腺原氨酸和甲状腺素浓度没有影响。试验结束时,Cr+犊牛的血糖浓度和胰岛素/血糖比值有升高的趋势。综上所述,铬在液体和固体饲料中的补充提高了夏季暴露犊牛的生长性能,这是由于呼吸率降低和采食量增加所致;然而,对饲料效率和胰岛素代谢没有有益的影响。