Dietary folic acid, uterine function and early embryonic development in sows

The present study was designed to determine the role of folic acid on uterine environment and embryonic development during early gestation in the pig. Thirty-two, third parity, crossbred sows received a diet supplemented with 0 or 15 mg kg-1 of folic acid. The treatments started 2 wk before expected estrus and lasted until slaughter on either day 12 or 15 after mating. One uterine horn was used to collect conceptuses and uterine "flushings" for hormonal and metabolite determinations; conceptuses from the other horn were enzymatically dispersed and placed in cell culture with and without dehydroepiandrosterone (DHEA). The decrease in serum folates was attenuated (P less than or equal to 0.06) and the total and saturated folate binding capacities in early gestation were increased (P < 0.01) in sows receiving additional dietary folic acid. The volume of uterine flushings recovered was greater (P less than or equal to 0.02) on day 15 than on day 12, as was its content of protein (P less than or equal to 0.06). In sows receiving the dietary supplement of folic acid, total uterine prostaglandin (PG)E2 was three times higher on day 12 and two times higher on day 15 (P < 0.04) than for sows fed the experimental diet without supplement; although numerically substantial (60% higher), the effect was not significant for PGF2 alpha (P greater than or equal to 0.16). Conceptus homogenates contained more folic acid (P less than or equal to 0.02) and DNA (P less than or equal to 0.0001) on day 15 than on day 12. Their total protein content, in sows slaughtered on day 12 of gestation, tended (P less than or equal to 0.07) to be higher in supplemented than in unsupplemented animals. The synthesis of estradiol-17beta by the conceptus cells, used as an index of embryonic maturity, tended (P less than or equal to 0.07) to be lower for treated than untreated sows, especially in conceptus cell culture without DHEA. Therefore, the improvement in embryonic survival attributed to dietary supplements of folic acid might be linked to changes on the secretion of uterine prostaglandins and possibly on embryonic development.