This study was undertaken to evaluate the relationship between plasma and milk concentrations of vitamin B₁₂ as well as the relationship between plasma or milk concentrations of vitamin B₁₂ and plasma concentration of free fatty acids (FFA) or blood concentration of β-hydroxybutyrate (BHB) of early lactating Ayrshire (AY) and Holstein (HO) cows. A total of 44 dairy herds (7 AY and 37 HO herds) and 62 AY (21 in first, 19 in second, and 22 in third and more lactations) and 228 HO (51 in first, 74 in second, and 103 in third and more lactation) cows between 3 and 40 d in milk were involved in the study. Hand-stripped milk samples and blood samples were taken 6 h after the morning milking. Milk and plasma samples were analyzed for vitamin B₁₂ concentration and plasma samples were analyzed for FFA concentration. A handheld device was used for blood BHB concentration determination. Thresholds for elevated plasma FFA concentration and hyperketonemia were set at ≥0.70 and ≥1.2 mmol/L, respectively. Vitamin B₁₂ concentration in milk of AY primiparous cows [2,557 (1,995–3,276) pg/mL] was lower than in milk from HO primiparous cows [3,876 (3,356–4,478) pg/mL], whereas no difference was observed among other parities and breeds. Regardless of breeds, plasma concentration of vitamin B₁₂ of first and second parities was lower than plasma concentration of third and more lactation cows. Milk vitamin B₁₂ concentration was positively correlated with plasma vitamin B₁₂ concentration, but the relationship was stronger for AY (ρ averaging 0.63) than for HO cows (ρ averaging 0.36). For AY and HO breeds, a significant relationship between milk or plasma vitamin B₁₂ concentrations and plasma FFA concentration (ρ between 0.29 and 0.59) was observed. Moreover, cows with elevated plasma FFA concentration had greater milk and plasma vitamin B₁₂ concentrations than cows with normal plasma FFA concentration. No relationship between vitamin B₁₂ concentration in milk or plasma and blood BHB concentration and hyperketonemia was noted. In summary, milk is not well correlated with plasma vitamin B₁₂ concentration for HO. It could be hypothesized that elevated plasma concentration of FFA could have a negative effect on the use of vitamin B₁₂ by cow cells, which increases the concentration of the vitamin in plasma and its secretion in milk.

进行这项研究是为了评估血浆和牛奶中维生素B _12的浓度之间的关系，以及血浆或牛奶中维生素B _12的浓度与血浆中游离脂肪酸（FFA）或血液中β-羟基丁酸酯（BHB）浓度之间的关系。）的早期哺乳期的爱尔郡（AY）和荷斯坦（HO）奶牛。共有44个乳牛群（7 AY和37 HO牛群）和62 AY（第一21个，第二19，第二22和第三和更多哺乳期）和228 HO（第一51个，第二74个和第三103个）泌乳时间在3到40天之间的母牛也参与了这项研究。早晨挤奶后6小时采集手剥的牛奶样本和血液样本。分析牛奶和血浆样品中的维生素B ₁₂浓度和血浆样品中的FFA浓度进行了分析。使用手持式设备确定血液中的BHB浓度。血浆FFA浓度升高和高血钾的阈值分别设置为≥0.70和≥1.2mmol / L。AY初产奶牛的牛奶中的维生素B ₁₂浓度[2,557（1,995–3,276）pg / mL]低于HO初产奶牛的牛奶中的维生素B ₁₂ [3,876（3,356–4,478）pg / mL]，而在其他胎龄中均未观察到差异和品种。无论哪个品种，第一胎和第二胎的维生素B ₁₂的血浆浓度均低于第三胎和更多泌乳牛的血浆浓度。牛奶中维生素B _12的浓度与血浆维生素B ₁₂呈正相关浓度，但AY的关系（ρ平均为0.63）比HO奶牛（ρ平均为0.36）更强。对于AY和HO品种，观察到牛奶或血浆中的维生素B ₁₂浓度与血浆FFA浓度之间存在显着关系（ρ在0.29至0.59之间）。此外，血浆FFA浓度升高的母牛比血浆FFA浓度正常的母牛具有更高的牛奶和血浆维生素B ₁₂浓度。牛奶或血浆中的维生素B ₁₂浓度与血中BHB浓度和高血钾症之间没有关系。总之，牛奶与血浆维生素B _12的相关性不高HO的浓度。可以假设，血浆中FFA的浓度升高会对牛细胞对维生素B ₁₂的使用产生负面影响，这会增加血浆中维生素的浓度及其在牛奶中的分泌。