232 EFFECT OF DIETARY FAT SUPPLEMENTATION ON OOCYTE AND EMBRYO QUALITY AND ON EARLY EMBRYONIC DEVELOPMENT OF SHEEP

Abstract

The objective was to evaluate the effect of fat supplementation on oocyte quality and in vitro embryonic development (48 h). A total of 18 ewes, with a body condition score of 2.5 to 3 points out of 5, having had three to four lamb births, and at three to four months post-lamb birth, were distributed between an experimental oil group (OG; n = 9) that received corn oil (4% of the MS/diet) and a control group (CG; n = 9) that didn't receive oil. The two groups were maintained in confinement for 21 days (the duration of the experiment) and fed first with a concentrate diet followed by forage. The animals had access to minerals and water ad libitum. The diets were similar in energy (10.3 ± 0.05 MJ/s/d) and protein (141.75 ± 5.7 gPC/s/d) for both groups. The estrous cycle was synchronized (14 days) with intravaginal sponges (40 mg of fluorogestone acetate), inserted 7 days after the beginning of the diets. The end of the diet coincided with the retirement of the sponges. One day before sponge retirement, 75 mg prostaglandin F2α per sheep was administered, followed by ovarian stimulation with 1000 IU of pregnant mare serum gonadotropin (PMSG). Follicular diameter was determined by ventral laparotomy with the aid of a micrometer. Follicles were classified as small (2 to 2.9 mm), medium (3 to 4.9 mm), and large (>5 mm); oocytes were collected in TCM-199 medium. Oocytes were classified as excellent, good, fair, or low quality and transferred to Petri dishes in drops (50 mL) of TCM-199. Oocytes were matured and fertilized in vitro and cultured for 48 h. Oocyte quality as well as maturation, fertilization, and cleavage rates were compared by ANOVA. Ewes from the OG group presented a statistically higher proportion of oocytes with excellent quality (42%; P < 0.05) than GT ewes (26%). The proportion of good quality and fair quality oocytes was similar among groups (P > 0.05). A higher proportion of oocytes of low quality was found in the control group than in the OG group (40% vs. 18%); however, there was no significant difference (P > 0.05). Higher rates of maturation, fertilization, and early development were found in the OG compared with the CG (81.8, 60.6, and 36.4 vs. 68.6, 42.9, and 17.1, respectively); however, the differences were not significant (P > 0.05). In conclusion, the addition of 4% corn oil in the diet improved the quality of the oocytes; however, it had no significant effect on early embryonic development.