The current study was conducted to investigate the effects of dietary supplementation of biotin, intramuscular injections of vitamin B₁₂ (VB₁₂), or both beginning at the prepartum period on feed intake and lactation performance in postpartum dairy cows. Forty-eight dairy cows were allocated into 12 blocks, based on parity and milk yield of the previous lactation cycle, and randomly assigned to 1 of 4 treatments. Supplementation of VB₁₂ (weekly intramuscular injections of 0 or 10 mg) and biotin (dietary supplements of 0 or 30 mg/d) were used in a 2 × 2 factorial arrangement in a randomized complete block design of 12 blocks with repeated measures. The study started at 3 wk before the expected calving date and ended at 8 wk after calving. Feed intake and lactation performance (milk yield and composition) were recorded weekly after calving. Blood variables were measured on d −10, 0, 8, 15, 29, 43, and 57 relative to calving. When VB₁₂ was given, the cows had greater feed intake, better lactation performance and lower body weight loss in the postpartum period compared with animals without injection of VB_12. The VB₁₂-injected cows had lower plasma nonesterified fatty acids and β-hydroxybutyrate concentrations but higher plasma superoxide dismutase activity compared with cows without VB₁₂. Cows fed a biotin supplement had higher milk protein yield (6 and 8 wk) and lactose yield (6–8 wk), compared with animals without biotin. However, under the present experimental conditions, we found no additive effect of a combined supplement of biotin and vitamin B₁₂ on lactation performance of dairy cows.

当前的研究旨在调查饮食中补充生物素，肌肉注射维生素B ₁₂（VB ₁₂）或从产前开始对产后奶牛采食量和泌乳性能的影响。根据前一个泌乳周期的胎次和产奶量，将48头奶牛分为12个区块，并随机分配给4种处理之一。VB _12的补充（每周肌肉注射0或10毫克）和生物素（饮食补充剂0或30毫克/天）以2×2析因排列方式使用，以12个区块为随机完整区块设计，并重复测量。研究在预期产犊日期之前的3周开始，在产犊之后的8周结束。产犊后每周记录一次采食量和泌乳性能（牛奶产量和组成）。相对于产犊，在d -10，0、8、15、29、43和57上测量血液变量。当VB ₁₂被给出时，奶牛具有更大的采食量，更好的泌乳性能和在产后期降低体重损失与动物不注射VB相比₁₂的VB ₁₂与未注射VB _12的母牛相比，注射牛的血浆非酯化脂肪酸和β-羟基丁酸酯浓度较低，但血浆超氧化物歧化酶活性较高。与没有生物素的动物相比，饲喂生物素补充剂的母牛的牛奶蛋白产量（6和8 wk）和乳糖产量（6-8 wk）更高。但是，在目前的实验条件下，我们没有发现生物素和维生素B ₁₂的联合补充对奶牛泌乳性能的累加作用。