167 Ovarian response and embryo production of cows superstimulated with different FSH regimens and inseminated with conventional or sex-sorted spermatozoa

The aim of this study was to evaluate ovarian response and embryo production of Holstein cows superstimulated either with constant or decreasing doses of FSH, and the effect of SexedULTRA 4M (STgenetics) field fertility sires on embryo outcomes and sperm traits. Four experiments were performed with non-lactating and lactating Holstein cows (2–6 years old). The superovulation (SOV) protocol was a modified Double-Ovsynch. In the D-FSH group, 300 mg of FSH (Folltropin-V) was distributed over 10 decreasing doses, 12 h apart; in the C-FSH group, 300 mg was distributed over 10 constant doses. Semen quality was assessed before insemination, which occurred 12 and 24 h after gonadotrophin-releasing hormone (GnRH), with conventional or SexedULTRA 4M semen, according to the experiments. Embryo collections were performed 7 days later. In Exp. 1, non-lactating cows (n = 18) underwent SOV with crossover of FSH regimens and were inseminated with conventional semen. In Exp. 2, in a 2 × 2 factorial arrangement, non-lactating cows (n = 14) underwent SOV with crossover of FSH. Part (20 SOV) had crossover of SexedULTRA semen, from sires classified as ultra-fertility (UF; higher field fertility, 3% pregnancy per AI above average at 60 days) or non-UF (NUF), whereas the remaining 30 SOV had no crossover of sire fertility. In Exp. 3 (n = 12; non-lactating) and 4 (n = 11; lactating), in 2 × 2 factorial arrangements, cows underwent SOV with the same FSH regimens (D- or C-FSH) and with crossover of SexedULTRA sires (UF vs. NUF). Statistical analyses were performed by Glimmix of SAS 9.4 (SAS Institute Inc.). Significant differences were considered when P ≤ 0.05 and a tendency when 0.05 < P ≤ 0.10. When data from all experiments were combined (n = 131), D-FSH produced greater number of follicles ≥8.5 mm than C-FSH (18.6 ± 1.1 vs. 13.2 ± 0.8), produced more CL (13.1 ± 0.9 vs. 10.4 ± 0.6), and tended to produce more ova and/or embryos (6.7 ± 0.7 vs. 4.9 ± 0.5). However, the percentage of cows with ≥2 transferable embryos did not differ. For donors with ≥2 structures recovered (n = 107), D-FSH produced more CL (14.7 ± 0.8 vs. 11.0 ± 0.6), ova and/or embryos (8.0 ± 0.7 vs. 6.0 ± 0.5), and degenerate embryos (2.1 ± 0.5 vs. 1.1 ± 0.2), compared with C-FSH. The number of transferable embryos (4.1 ± 0.5 vs. 3.2 ± 0.3), freezable embryos (3.4 ± 0.4 vs. 2.6 ± 0.3), and unfertilised ova were similar between regimens. Combined results from all donors (n = 96) had no effect of field fertility sires (n = 6 UF and 6 NUF). However, for donors with ≥2 structures recovered (n = 76), UF sires yielded more transferable embryos (4.4 ± 0.5 vs. 2.6 ± 0.4) and freezable embryos (4.0 ± 0.5 vs. 2.1 ± 0.4), and greater percentages of transferable and freezable embryos. Moreover, UF sires produced fewer unfertilised oocytes (1.2 ± 0.3 vs. 3.1 ± 0.6) and had greater progressive motility (55.3 ± 1.6 vs. 46.4 ± 1.9%). In conclusion, although decreasing doses of FSH were superior in superstimulation, the production of viable embryos was similar to constant doses. Overall combined results indicated that UF sires were better in embryo yield; however, wide variability among bulls still exists.

This research was supported by FAPESP 2018/03798-7, Sexing Technologies (Brazil), and Vetoquinol.