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 i n the pig. Thirty-two, third parity, crossbred sows received a diet su pplemented with 0 or 15 mg kg(-1) of folic acid. The treatments starte d 2 wk before expected estrus and lasted until slaughter on either day 12 or 15 after mating. One uterine horn was used to collect conceptus es and uterine ''flushings'' for hormonal and metabolite determination s; conceptuses from the other horn were enzymatically dispersed and pl aced in cell culture with and without dehydroepiandrosterone (DHEA). T he decrease in serum folates was attenuated (P less than or equal to 0 .06) and the total and saturated folate binding capacities in early ge station 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 conte nt of protein (P less than or equal to 0.06). In sows receiving the di etary supplement of folic acid, total uterine prostaglandin (PG)E(2) w as 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; althou gh numerically substantial (60% higher), the effect was not significan t for PGF(2 alpha) (P greater than or equal to 0.16). Conceptus homoge nates 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 tota l 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 un supplemented animals. The synthesis of estradiol-17 beta by the concep tus 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, especi ally in conceptus cell culture without DHEA. Therefore, the improvemen t in embryonic survival attributed to dietary supplements of folic aci d might be linked to changes on the secretion of uterine prostaglandin s and possibly on embryonic development.