Composition of follicular fluid and serum, ovarian dynamics, and IGF-1 concentrations following n-3 fatty acid supplementation in mares

Abstract Text:

The effects of a marine-derived n-3 fatty acid supplement on ovarian dynamics and follicular fluid and serum composition were evaluated during the estrous cycle in mares. Fifteen mares were assigned to a control diet (CONT, n = 7) or a fish oil-enriched diet (FO, n = 8) providing 18.48 g eicosapentaenoic acid (EPA) and 10.08 g docosahexaenoic acid (DHA) daily. Follicular activity was determined via transrectal ultrasonography at the initiation of the treatment diet. Estrous cycles were synchronized in all mares concurrently with initiation of treatment diets using a progesterone and estradiol protocol. Following ovulation post-synchronization, mare monitoring continued through the second estrous cycle. Ovarian activity, timing of ovulation, and presence of a corpus luteum were recorded. Mares were scanned during the third estrous cycle until a 35 mm follicle was detected, at which time hCG was administered. A transvaginal ultrasound-guided follicular aspiration (TUGA) was performed on the largest preovulatory follicle 14-16 h post-hCG. Follicular fluid was analyzed for fatty acids, estradiol 17-β, LH, progesterone, PGF_2α, PGE₂, and IGF-1 concentrations. Serum samples were collected at the onset of treatment diet and every 2 wk until termination of the study to determine fatty acid concentrations. Additional serum samples were obtained prior to hCG administration and prior to TUGA procedure for measurement of IGF-1. Arachidonic acid (ARA), EPA, docosapentaenoic acid (DPA), and DHA in mare serum and EPA, DPA, and DHA in follicular fluid were increased (P < 0.01) in the FO group. Serum IGF-1 was decreased (P < 0.05) in the FO group immediately prior to aspiration. Concentrations of IGF-1 were decreased (P < 0.05) in follicular fluid in the FO group compared with controls. No other differences in follicular fluid hormone concentrations were detected. Follicular growth rate, ovulation interval, and timing of ovulation were similar between groups.  These data indicate that in addition to incorporation into serum, dietary n-3 fatty acids can also be incorporated into follicular fluid, and may have an inhibitory effect on serum and follicular fluid IGF-1 concentrations in the cycling mare. 

Keywords: mare, n-3, follicular fluid