Combined biotin, folic acid, and vitamin B supplementation given during the transition period to dairy cows: Part I. Effects on lactation performance, energy and protein metabolism, and hormones.

Biotin (B), folates (B), and vitamin B (B) are involved and interrelated in several metabolic reactions related to energy and protein metabolism. We hypothesized that a low supply of one of the latter vitamins during the transition period would impair metabolic status. The purpose of this study was to evaluate the effect of B supplementation on the response of lactation performance and selected energy and protein metabolites and hormones to a combined supplementation of B and B given to periparturient dairy cows, from d -21 to 21 relative to calving. A total of 32 multiparous Holstein cows housed in tie stalls were randomly assigned, according to their previous 305-d milk yield, to 8 incomplete blocks of 4 treatments: (1) a 2-mL weekly i.m. injection of saline (0.9% NaCl; B-/BB-); (2) 20 mg/d of dietary B (unprotected from ruminal degradation) and 2-mL weekly i.m. injection of 0.9% NaCl (B+/BB-); (3) 2.6 g/d of dietary B (unprotected) and 2-mL weekly i.m. injection of 10 mg of B (B-/BB+); and (4) 20 mg/d of dietary B, 2.6 g/d of dietary B, and weekly i.m. injection of 10 mg of B (B+/BB+) in a 2 × 2 factorial arrangement. Milk yield and dry matter intake were obtained daily and milk components weekly. Blood samples were taken weekly from d -21 to calving and 3 times per week from calving to 21 d following parturition. Prepartum plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), and adiponectin were unaffected by treatments. Biotin, B, and B supplements increased their respective concentrations in plasma and milk. Cows fed the B supplement tended to have lower dry matter intake, but only cows in B+/BB- had greater plasma concentrations of NEFA compared with B-/BB-. Milk and total solid yields were greater by 13.5 and 13.9%, respectively, for B-/BB+ [45.5 (standard error, SE: 1.8) and 5.81 (0.22) kg/d, respectively] compared with B-/BB- [40.1 (1.9) and 5.10 (0.23) kg/d, respectively], but these effects were suppressed when combined with the B supplement. Cows in the B-/BB+ group had decreased plasma insulin and tended to have increased NEFA concentrations, but postpartum plasma concentrations of glucose, BHB, leptin, and adiponectin were not affected. These cows also mobilized more body fat reserves, as suggested by a tendency to increased plasma NEFA and more milk total solids compared with B-/BB- cows. However, plasma concentrations of BHB and adiponectin were similar among treatments. This suggests that the B and B supplements enhanced efficiency of energy metabolism in early lactation cows. Folic acid and B supplementation increased postpartum plasma Cys and homocysteine concentrations but did not affect plasma Met concentration, suggesting an upregulation of the transsulfuration pathway. In summary, our results showed that, under the current experimental conditions, increasing B supply did not improve responses to the B and B supplementation.