Combined biotin, folic acid, and vitamin B supplementation given during the transition period to dairy cows: Part II. Effects on energy balance and fatty acid composition of colostrum and milk.

Biotin (B), folate (B), and vitamin B (B) are involved in several metabolic reactions related to energy metabolism. We hypothesized that a low supply of one of these vitamins during the transition period would impair metabolic status. This study was undertaken to assess the interaction between B supplement and a supplementation of B and B regarding body weight (BW) change, dry matter intake, energy balance, and fatty acid (FA) compositions of colostrum and milk fat from d -21 to 21 relative to calving. Thirty-two multiparous Holstein cows housed in tie stalls were randomly assigned, according to their previous 305-d milk yield, to 8 incomplete blocks in 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+); (4) 20 mg/d of dietary B, 2.6 g/d of dietary B, and 2-mL weekly i.m. injection of 10 mg of B (B+/BB+) in a 2 × 2 factorial arrangement. Colostrum was sampled at first milking. and milk samples were collected weekly on 2 consecutive milkings and analyzed for FA composition. Body condition score and BW were recorded every week throughout the trial. Within the first 21 d of lactation, B-/BB+ cows had an increased milk yield by 13.5% [45.5 (standard error, SE: 1.8) kg/d] compared with B-/BB- cows [40.1 (SE: 1.9)], whereas B supplement had no effect. Even though body condition score was not affected by treatment, B-/BB+ cows had greater BW loss by 24 kg, suggesting higher mobilization of body reserves. Accordingly, milk de novo FA decreased and preformed FA concentration increased in B-/BB+ cows compared with B-/BB- cows. In addition, cows in the B+/BB- group had decreased milk de novo FA and increased preformed FA concentration compared with B-/BB- cows. Treatment had no effect on colostrum preformed FA concentration. Supplemental B decreased concentrations of ruminal biohydrogenation intermediates and odd- and branched-chain FA in colostrum and milk fat. Moreover, postpartum dry matter intake for B+ cows tended to be lower by 1.6 kg/d. These results could indicate ruminal perturbation caused by the B supplement, which was not protected from rumen degradation. Under the conditions of the current study, in contrast to B+/BB- cows, B-/BB+ cows produced more milk without increasing dry matter intake, although these cows had greater body fat mobilization in early lactation as suggested by the FA profile and BW loss.