Pre- and post-mating dietary supplements of folic acid and uterine secretory activity in gilts

The present study was carried out to determine the effects of pre- and (or) post-mating dietary supplements of folic acid on uterine secretions and secretory activity on day 12 of gestation. Crossbred gilts were assigned randomly to three treatments: SS) a dietary supplement of 15 mg of folic acid kg −1 of diet from the estrus before mating (approximately day –21) until day 12 of gestation (n = 9), 0S) the same folic acid supplement from mating (day 0) to day 12 of gestation (n = 10), and 00) no supplement of folic acid (n = 10). At slaughter (day 12 of gestation), one uterine horn was flushed with 20 mL of PBS to collect embryos and uterine flushings, while samples of uterine tissue were collected from the other horn. Supplementary folic acid (0S and SS) increased total folates in uterine flushings (P ≤ 0.05) as well as concentrations of folates in the endometrium (P ≤ 0.0004) and in the whole uterine tissue (endometrium + myometrium: P ≤ 0.0001). Total amounts of prostaglandin (PG)E 2 and PGF 2α in uterine flushings were not affected (P ≥ 0.8) by any treatment but estradiol-17β was numerically 40% lower (P ≥ 0.12) in uterine flushings of 0S and SS sows. Samples of endometrium (15–17 mg) were cultured for 2 to 7 h. Concentrations of PGE 2 and PGF 2α in the culture medium increased with the duration of incubation (P ≤ 0.0001) but there was no treatment effect (P ≥ 0.4). The inconsistency between the folic acid response seen in the present study and in previous results using multiparous sows suggests that the impact of this vitamin on sow reproduction might be linked to the parity (and/or prolificacy) of the animal. Key words: Folic acid, uterine tissue, secretion, prostaglandins, gilts