The objective of this study was to evaluate the effects of 25-hydroxyvitamin D₃ on the lactation performance, blood metabolites, and antioxidant and immune function in dairy cows. Thirty-six mid-lactation Holstein dairy cows were blocked according to day in milk, milk yield and somatic cell counts (SCC) and were randomly assigned to 3 treatments. Treatments were a basal diet plus 0 mg, 1 mg or 3 mg 25-hydroxyvitamin D₃ per cow per day throughout a 9-week trial period. Cows were milked three times daily, and dry matter intake and milk yield were measured daily. Milk components were sampled at days 0, 21, 42 and 63 for milk fat, protein, lactose and SCC analysis. Blood was sampled for blood metabolites, parameters of antioxidant and immune function at days 0, 21, 42 and 63. Dairy cows fed 25-hydroxyvitamin D₃ showed linear increases (P < 0.05) in milk yield, energy-corrected milk, milk protein and lactose yield and a decrease in somatic cell counts in milk (P < 0.01). Feeding dietary 25-hydroxyvitamin D₃ linearly increased serum total Ca, P, 25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ and had no negative effect on blood biochemical parameters and markers of fat mobilization. Additionally, dietary 25-hydroxyvitamin D₃ linearly increased (P < 0.05) total antioxidant capacity, total superoxide dismutase, glutathione peroxidase, immunoglobulin A and immunoglobulin G and linearly decreased (P < 0.05) malondialdehyde and tumor necrosis factor-α. In summary, dietary supplementation with 25-hydroxyvitamin D₃ increased milk yield and decreased SCC, improved serum minerals, 25-hydroxyvitamin D₃ levels, and antioxidant and immune function of dairy cows.

这项研究的目的是评估25-羟基维生素D ₃对奶牛泌乳性能，血液代谢产物以及抗氧化剂和免疫功能的影响。根据天数将三十六头荷斯坦奶牛按乳，奶产量和体细胞计数（SCC）的天数封锁，并随机分配给3种处理方法。治疗方法是基础饮食加0 mg，1 mg或3 mg 25-羟基维生素D ₃在9周的试用期内，每天每头奶牛。母牛每天要挤奶3次，每天要测量干物质的摄入量和产奶量。在第0、21、42和63天对牛奶成分进行采样，以进行牛奶脂肪，蛋白质，乳糖和SCC分析。在第0、21、42和63天对血液进行了血液代谢产物，抗氧化剂和免疫功能参数的采样。饲喂25-羟基维生素D _3的奶牛的牛奶产量，能量校正的牛奶，牛奶蛋白质呈线性增加（P <0.05）牛奶中乳糖的产量和体细胞计数的减少（P <0.01）。饲喂饮食中的25-羟基维生素D ₃线性增加血清总Ca，P，25-羟基维生素D ₃和1,25-二羟基维生素D ₃并且对血液生化参数和脂肪动员指标没有负面影响。此外，饮食中的25-羟基维生素D ₃线性增加（P <0.05）总抗氧化剂能力，总超氧化物歧化酶，谷胱甘肽过氧化物酶，免疫球蛋白A和免疫球蛋白G并线性下降（P <0.05）丙二醛和肿瘤坏死因子-α。总之，膳食补充25-羟基维生素D _3可以增加产奶量并降低SCC，改善血清矿物质，25-羟基维生素D _3的含量，并能提高奶牛的抗氧化和免疫功能。