The effect of 10% dietary flaxseed fed for 3 and 6 weeks on serum hormone levels of fattening gilts, the fatty acid (FA) follicular fluid (FF) composition of small and large antral follicles, and the steroidogenesis and IGF-I secretion by isolated small antral follicles and their response to regulatory hormones (LH, FSH, IGF-I) was studied using immunoassay and gas chromatography analyses. Both supplemental periods increased levels of P4 and IGF-I in blood serum. A shorter period inhibited steroidogenesis (P4, T, E2) and IGF-I secretion by small antral follicles, which was associated with decreased levels of monounsaturated FAs (MUFA) and preferred n-6 polyunsaturated FA (PUFA) metabolism. A longer period stimulated hormone secretion at elevated levels of saturated FAs (SFA) at the expense of MUFAs and PUFAs preferring the n-3 PUFA metabolism. Out of ovarian regulators, only LH and IGF-I were able to alter the secretion of steroids and IGF-I by small follicles of fattening pigs fed a basal diet. The effect of flaxseed on the secretion of follicular hormones after both supplemental periods was altered by all regulatory hormones in a dose-dependent manner. The level of SFAs and PUFAs in FF of large follicles increased with the length of flaxseed feeding, suggesting the suppression of ovulation.
Keywords: IGF-I; dietary flaxseed; fatty acid; follicular fluid; gonadotropins; porcine ovary; steroids.