USDA, ARS, National Animal Disease Center, Periparturient Diseases of Cattle Research Unit, PO Box 70, Ames, IA 50010, USA.
J Dairy Sci. 2009 Dec;92(12):6134-43. doi: 10.3168/jds.2009-2517.
The physiological response of the preruminant calf to sustained exposure to moderate cold has not been studied extensively. Effects of cold on growth performance and health of preruminant calves as well as functional measures of energy metabolism, fat-soluble vitamin, and immune responsiveness were evaluated in the present study. Calves, 3 to 10 d of age, were assigned randomly to cold (n = 14) or warm (n = 15) indoor environments. Temperatures in the cold environment averaged 4.7 degrees C during the study. Frequent wetting of the environment and the calves was used to augment effects of the cold environment. Temperatures in the warm environment averaged 15.5 degrees C during the study. There was no attempt to increase the humidity in the warm environment. Preventative medications or vaccinations that might influence disease resistance were not administered. Nonmedicated milk replacer (20% crude protein and 20% fat fed at 0.45 kg/d) and a nonmedicated starter grain fed ad libitum were fed to all calves. Relative humidity was, on average, almost 10% higher in the cold environment. Warm-environment calves were moderately healthier (i.e., lower respiratory scores) and required less antibiotics. Scour scores, days scouring, and electrolyte costs, however, were unaffected by environmental temperature. Growth rates were comparable in warm and cold environments, although cold-environment calves consumed more starter grain and had lower blood glucose and higher blood nonesterified fatty acid concentrations. The nonesterified fatty acid and glucose values for cold-stressed calves, however, did not differ sufficiently from normal values to categorize these calves as being in a state of negative-energy balance. Levels of fat-soluble vitamin, antibody, tumor necrosis factor-alpha, and haptoglobin were unaffected by sustained exposure to moderate cold. These results support the contention that successful adaptation of the dairy calf to cold is dependent upon the availability of adequate nutrition.
反刍前小牛对持续暴露于适度寒冷的生理反应尚未得到广泛研究。本研究评估了寒冷对反刍前小牛的生长性能和健康的影响，以及能量代谢、脂溶性维生素和免疫反应的功能措施。3 至 10 日龄的小牛随机分配到寒冷（n = 14）或温暖（n = 15）室内环境中。研究期间，寒冷环境的平均温度为 4.7°C。频繁淋湿环境和小牛以增强寒冷环境的影响。研究期间，温暖环境的平均温度为 15.5°C。没有试图增加温暖环境的湿度。未使用可能影响疾病抵抗力的预防性药物或疫苗。所有小牛均喂食非药物牛奶代用品（20%粗蛋白和 20%脂肪，每天 0.45 公斤）和非药物起始谷物自由采食。相对湿度在寒冷环境中平均高出近 10%。温暖环境中的小牛健康状况较好（即，较低的呼吸道评分），抗生素用量较少。然而，腹泻评分、腹泻天数和电解质成本不受环境温度的影响。在温暖和寒冷环境中，生长速度相当，尽管寒冷环境中的小牛消耗更多的起始谷物，血糖较低，非酯化脂肪酸浓度较高。然而，寒冷应激小牛的非酯化脂肪酸和血糖值并未低到足以将这些小牛归类为处于负能平衡状态。脂溶性维生素、抗体、肿瘤坏死因子-α和触珠蛋白的水平不受持续暴露于适度寒冷的影响。这些结果支持以下论点，即奶牛小牛成功适应寒冷取决于充足的营养供应。
