Biotin, folic acid, and vitamin B12 supplementation given in early lactation to Holstein dairy cows: Their effects on whole-body propionate, glucose, and protein metabolism

Biotin (B8), folic acid (B9), and vitamin B12 (B12) play key roles in energy and protein metabolism. The aim of this study was to evaluate the effects of a B8 supplement, administered alone or combined with B9 and B12 during the transition period on glucose, propionate, and protein metabolism. Thirty-two Holstein multiparous cows were assigned to one of the 4 treatments according to an incomplete block design in a 2 × 2 factorial arrangement: 1) 2-mL of weekly intramuscular injections of saline 9 g/L NaCl (B8 −/B9B12 −); 2) 20 mg/d of dietary B8 (unprotected from ruminal degradation) and 2-mL weekly intramuscular injections of saline 9 g/L NaCl (B8 +/B9B12 −); 3) 2.6 g/d of dietary B9 (unprotected) and 2-mL weekly intramuscular injections of 10 mg of B12 (B8 −/B9B12 +); 4) 20 mg/d of dietary B8, 2.6 g/d of dietary B9 and weekly intramuscular injections of 10 mg of B12 (B8 +/B9B12 +). Treatments were given from − 26–45 days relative to calving date. At 43 (SD:3) days in milk (DIM), D-[6,6-2H2]-glucose (23.9 mmol/h; jugular vein) and [1-13C]-sodium propionate (22.7 mmol/h; ruminal vein) were simultaneously infused for 4 h; the following 2 d, respectively, [13C]-sodium bicarbonate (3.0 mmol/h) and L[1-13C]-Leu (3.7 mmol/h) were infused into a jugular vein for 4 h. Blood samples were collected every 15 min during the last 1.5 h of infusions at 43 DIM and every 20 min at 44 and 45 DIM during the last 2 h of infusions. During the infusion week, there were no treatment effects on milk yield and major milk components, on whole-body propionate (1354 ± 116 mmol/h) and glucose (811 ± 34 mmol/h) rates of appearance, and on the proportion of glucose synthesized from propionate (65.1 ± 4.0%). Nevertheless, plasma glucose concentration during the infusions at 43 DIM for cows receiving the B8 supplement was greater when given in combination with B9 and B12, whereas no effect was noted without B8 supplementation. Whole-body Leu rate of appearance, Leu oxidation, and Leu used for protein synthesis and exportation averaged 133 ± 5, 23 ± 2, 111 ± 4, and 53 ± 2 mmol/h, respectively, and were not different among treatments. The present results might indicate that at the time of infusions between 43 and 45 days in milk under the current conditions, supplies of B8, B9, and B12 were sufficient to meet cow requirements. This reinforces the need to better define under which conditions cows would likely benefit from a supplementation caused by an imbalance between supplies and needs.