Supplemental folic acid: a requirement for optimizing swine reproduction.

The administration of supplemental folic acid to female reproducing swine (either via injection or dietary supplementation) is a fairly recent research phenomenon. The majority of publications have occurred during the past 5 yr; few publications on this topic appeared before 1983. Although folic acid supplementation is a young research area compared to that involving many other vitamins, the reported results are quite consistent. There seem to be no major benefits to lactational supplementation; although supplementation in lactation is effective in elevating sow serum folate, milk folate, and nursing pig serum folate, it has not produced changes in sow BW, litter size weaned, or pig gain. Supplementation during gestation has yielded a consistent benefit: a positive response in total pigs born in all studies. The response in gestation of increased litter size seems to be a result of improved embryo or fetal survival rather than increased ovulation, although the mechanism whereby survival rate is improved is yet to be understood. Clearly, supplemental folic acid is required to maximize sow prolificacy.