Effects of concentrations of cyanocobalamin in the gestation diet on some criteria of vitamin B12 metabolism in first-parity sows.

In swine nutrition, little is known about the role of vitamin B(12) in the reproductive processes. The current study was undertaken to obtain information on the dose-response pattern of different metabolic criteria related to the homeostasis of vitamin B(12) and homocysteine in gestating sows receiving various concentrations of dietary vitamin B(12) (cyanocobalamin). Homocysteine is a detrimental intermediate metabolite of the vitamin B(12)-dependent remethylation pathway of Met. Forty nulliparous (Large White x Landrace) sows were randomly assigned during gestation to dietary treatments containing 5 concentrations of cyanocobalamin (0, 20, 100, 200, or 400 microg/kg). During lactation, a diet containing 25 microg of cyanocobalamin/kg (as-fed) was given to all sows. During gestation, plasma vitamin B(12) increased as concentrations of dietary cyanocobalamin increased (linear and quadratic, P < 0.01) and the effect persisted during lactation (21 d postpartum) both in plasma (linear and quadratic, P < 0.05) and the liver (linear and quadratic, P < 0.04). Plasma homocysteine decreased with concentrations of cyanocobalamin provided to sows during gestation (linear, quadratic, and cubic, P < 0.01). At parturition, vitamin B(12) in colostrum increased as concentrations of cyanocobalamin increased (linear and quadratic, P < 0.01), but the treatment effect persisted (linear, P = 0.01) only up to 1 d postfarrowing. However, in piglets there was no treatment effect (P = 0.59) on plasma vitamin B(12) before colostrum intake, but a linear effect of concentrations of cyanocobalamin (P = 0.04) was observed 1 d later. Plasma homocysteine in piglets during lactation decreased with increasing concentrations of cyanocobalamin given to sows in gestation (linear and quadratic, P < 0.01). Based on a broken-line regression model, the concentrations of dietary cyanocobalamin that maximized plasma vitamin B(12) and minimized plasma homocysteine of sows during gestation were estimated to be 164 and 93 microg/kg, respectively. The maximal residual responses in sows and piglets during lactation were observed with treatments of 100 or 200 microg of cyanocobalamin/kg. The dietary cyanocobalamin concentration necessary to optimize the response of these metabolic criteria remains to be refined within lower and narrower ranges of cyanocobalamin concentrations (i.e., <200 mg/kg). Moreover, the biological significance of such concentrations of cyanocobalamin needs to be validated with performance criteria by using greater numbers of animals during several parities.