Effects of supplements of folic acid, vitamin B12, and rumen-protected methionine on whole body metabolism of methionine and glucose in lactating dairy cows.

摘要: The present experiment was undertaken to determine the effects of dietary supplements rumen-protected methionine and intramuscular injections folic acid vitamin B(12), given 3 wk before 16 after calving, on glucose metabolism lactating dairy cows. Twenty-four multiparous Holstein cows were assigned 6 blocks 4 each according their previous milk production. Within block, 2 fed a diet estimated supply as 1.83% metabolizable protein, equivalent 76% requirement, whereas other same supplemented daily with 18 g methionine. diet, administrated either no supplement or weekly 160 mg plus 10 B(12.) To investigate metabolic changes at 12 lactation, kinetics measured by isotope dilution using infusions 3[U-(13)C]glucose, [(13)C]NaHCO(3) 3[1-(13)C,(2)H(3)] Milk plasma concentrations B(12) increased injections. Supplementary B-vitamins production from 34.7 38.9 +/- 1.0 kg/d lactose, total solids yields. Whole-body flux tended increase supplementation similar quantitative magnitude lactose yield increase. Vitamin utilization for protein synthesis through turnover when deficient decreased oxidation fed. homocysteine independently feeding, although effect remethylation, but this could be due limitation technique used. Therefore, these lactation performance not mainly explained economy because more efficient methylneogenesis rather related availability in metabolism.