Effects of purified eCG concentration in eCG/pgf2 based sov protocols on ovarian structures and in vivo embryo production in Nelore cattle

ARRESEIGOR, C.; GUTIÉRREZ REINOSO, M.A. ; KONRAD, J.L.; MALDONADO VARGAS, P; GARCÍA HERREROS, M.

Bologna

Congreso; 19th International Congress on Animal Reproduction; 2022

ICAR

Superovulation (SOV) is a frequent approach to maximize the number of embryos available per individual for increasing profitability and genetic gains in bovine species. The main aim was to study the effect of different purified eCG (eCG-p) concentrations in eCG/PGF2α-based SOV protocols in order to test the differential effects obtained regarding ovarian structures and in vivo embryo production in Nelore (Bos indicus) cattle. A total of 24 Nelore cows (BC: 3-3.5) were divided randomly into 2 groups: NH (n=12; high eCG-p dose= 2,500 IU) and NL (n=12; low eCG-p dose= 2,000 IU). The SOV protocol was applied as follows: Day 0: intravaginal P4 device (CIDR: 1.38 gr) + 2 mg intramuscular (i.m.) Estradiol Benzoate E2B + 50 mg P4 (i.m.); Day 4: eCG-p (2,500 or 2,000 IU for NH and NL group, respectively); Day 6: PGF2α i.m. (300 μg D-cloprostenol); Day 7: CIDR removal (36h post- 1st PGF2α application) + PGF2α i.m. (150 μg D-cloprostenol); Day 8: 500 μg GnRH (48h post-1st PGF2α application) + FTAI. Ovarian structures (follicles (FL) and corpora lutea (CL)) were recorded by ultrasonography on Day 8 and Day 15 (embryo collection day). The traits assessed were: total follicles (TFL > 8mm), total corpora lutea (TCL), and no-ovulated follicles (NOFL). Embryo-derived parameters were: ovulation rate (OR; %), recovery rate (RR; %), total structures (TS), transferable embryos (TE), freezable embryos (FE), unfertilized oocytes (UFOs) and degenerated structures (DS). No differences were observed in TFL, TCL or NOFL ovarianderived traits between groups (p>0.05). Significant differences were observed in OR (40.8±6.0% vs. 58.4±5.3%), TE (4.4±0.6 vs. 6.9±1.0), and FE (3.8±0.7 vs. 6.7±0.9) embryoderived traits for NH and NL, respectively (p0.05). In conclusion, although no differences were observed regarding ovarian-derived parameters between protocols, the most efficient eCG/PGF2α-based SOV protocol regarding embryo-derived traits was the low-eCG-pdose protocol (NL group) providing a higher number of transferable and freezable embryos per individual in Nelore breed cows.