197 Effect of follicle-stimulating hormone administered during different time intervals in superovulation protocols in beef cattle

Multiple ovulation and embryo transfer (MOET) is a biotechnology widely used for genetic improvement in cattle; however, there is great variability in donor response. Differences between management, genotype, environmental conditions, among other factors, can affect MOET results. The traditional protocols consist of 8 twice-daily FSH applications in decreasing dosages over 4 days. Reducing donor handling during MOET is an alternative for embryo production. The aim of this research was to evaluate a simplified protocol, testing single daily administrations of FSH over 4 days, without modifying the total dose calculated for treatment. The study was conducted in northern Mexico. Beef cattle donors (n=30) were used, 15 with control treatment (CT) and 15 with simplified treatment (ST). All donors were examined beforehand, focusing on the reproductive tract and body score condition, i.e. 5 to 7 (scale of 1-9). Intravaginal devices (IVD) Dispocel Max (Von Franken, Buenos Aires, Argentina) with 1.2g of progesterone were inserted and 2.5mg of oestradiol benzoate (Internacional Prode, Mexico) IM was applied on Day 0; FSH (Folltropin-V, Vetoquinol, Lure, France), applications were started on day 4. For CT, the FSH administration was done twice daily (at a 12-h interval), in 8 decreasing doses, and 150µg of D-cloprostenol (D-CLO; Prostagenol-D, International Prode, Guadalajara, Mexico) was administered IM in the morning and afternoon of Day 6. In the ST, donors were treated with once-daily injections of decreasing doses of FSH over 4 days, and 150µg of D-CLO was administered IM on Days 6 and 7. The IVD were removed on Day 7 and oestrus was detected using heat detection patches. Artificial insemination was performed using conventional frozen semen at 12, 20, and, in case of persistent heat, 30h after oestrus detection. Embryo collection was performed 7 days after insemination. The ovarian response was assessed by counting the corpora lutea (CL) detected by ultrasound. Embryo collection was performed by closed method. Analysis of variance was used with the GLM procedure in SAS software (version 9.3; SAS Institute Inc., Cary, NC, USA), to evaluate the results of ST compared with CT (α-level=0.05). The cattle breed and ranch identification were considered in the analyses. The number of CL in ST and CT was 6.8±1.6 and 8.8±1.5, respectively. The number of oocytes/embryos recovered in ST and CT were 7.3±3.0 and 11.4±2.7, respectively. The number of viable embryos (transferred or frozen) in ST and CT were 2.6±1.7 and 4.7±1.6, respectively. The number of unfertilized oocytes were 2.8±1.5 in ST and 4.2±1.3 in CT. The number of degenerated embryos in the ST were 2.0±1.1 and 1.0±1.0 in the CT. There were no significant differences between groups (P>0.05) for all variables analysed. Although the number of transferable embryos was numerically higher in the CT group, differences were not significant. Nevertheless, ST can be an alternative superovulation protocol, because working once a day saves time and facilitates the implementation of the MOET technique.