196 Embryo production using follicle-stimulating hormone (FSH) or FSH+equine chorionic gonadotropin in beef donors

The objective of the present study was to evaluate the superovulatory response and embryo production in beef donors using 8 twice-daily injections of FSH or an alternative protocol in which the last 4 FSH injections were replaced with a single injection of eCG. In Exp. 1, 12 mature Bonsmara donor cows, with a body condition score between 3 and 4 (1 to 5 scale) were superstimulated twice every 46 days in a crossover design (i.e. in each experiment all cows received 2 treatments and the 2 treatments were equally represented in each replicate). On Day 0 a.m., all donors received an intravaginal device with 1.2g of progesterone (Diprogest 1200®, Zoovet, Santa Fe, Argentina), along with 50mg of progesterone i.m (Progestar®, Zoetis, Buenos Aires, Argentina) and 5mg of oestradiol-17β (17βOestradiol®, Rio de Janeiro, Argentina) IM. On Day 4 a.m., the superstimulatory treatments were initiated and donors in the control group received 8 applications of FSH (Folltropin-V, Vetoquinol, Lure, France), IM (total dose: 300mg NIH-FSH-P1) in a twice-daily decreasing dosage schedule over 4 days (i.e. 60, 60, 50, 50, 30, 30, 10, and 10mg, respectively). Donors in the FSH+800 eCG group received only the first 4 applications of FSH (i.e. 60, 60, 50 and 50mg, respectively) and on Day 6 a.m. they received 800IU of eCG (Novormón®, Zoetis) IM in a single dose. All donors received 500μg of cloprostenol (Ciclase DL®, Zoetis) IM on Day 6 a.m. and p.m., and the intravaginal devices were removed on Day 7 a.m. All cows also received 100μg of gonadorelin acetate (GnRH, Gonasyn gdr, Zoetis) on Day 8 a.m. and were inseminated with frozen-thawed semen from 2 bulls 12 and 24h later. On Day 15, ova/embryos were collected and evaluated according to the IETS standards. The data were analysed by GLMM (Infostat, 2018). In Exp 2., 18 Bonsmara donors with similar conditions as those in Exp. 1 were superovulated twice in a crossover design. Cows in both groups received similar treatments to those in the FSH+eCG treatment of Exp. 1, except that the total dosage of FSH was 200mg (i.e. 60, 60, 40, and 40mg, respectively) and the eCG given on Day 6 a.m. was either 600IU (group 1) or 800IU (group 2). In Exp 1., the FSH (control) group had a higher (P