14 Effect of breed on oocyte recovery and embryo production following ovum pickup and fertility outcomes after transferring fresh in vitro-produced embryos
G. Lamberti A , H. Sadeghi A , M. Fernandes B , S. Filho B , J. Marchizeli B , R. Knychala B , M. Lucy C and J. Moraes AA Department of Animal and Food Sciences, Oklahoma State University, Stillwater, Oklahoma, USA
B Vale do Embrião, Uberlandia, Minas Gerais, Brazil
C Division of Animal Sciences, University of Missouri, Columbia, Missouri, USA
Reproduction, Fertility and Development 35(2) 132-133 https://doi.org/10.1071/RDv35n2Ab14
Published: 5 December 2022
© 2023 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Bos taurus and Bos indicus cattle are known for inheriting physiological differences such as thermal tolerance, growth rate, and milk production. Producers from tropical countries often use B. taurus × B. indicus crossbreeding for increasing heat and parasite tolerance while retaining the superior productive traits of B. taurus. The objective was to evaluate cumulus-oocyte complex (COC) recovery rate and embryo production metrics in B. indicus (Nelore and Gir), B. taurus (Senepol and Holstein), and B. indicus/B. taurus cross-bred (Brangus and Girolando) donor cows (n = 861) subjected to ovum pickup (OPU) and in vitro embryo production (IVP). Field fertility data from January to December 2019, including data from 1,500 OPU procedures and 45,738 retrieved COCs, was provided by a southeastern Brazilian IVF company. Data were analysed using linear mixed models with SAS (version 9.4; SAS). Continuous data were assessed for normality using the UNIVARIATE procedure and log-transformed if not normally distributed. All models included the fixed effect of breed (or species) and season, and the random effect of donor. Pearson correlation was calculated using PROC CORR. Statistical significance was defined as P = 0.05 and statistical tendencies as 0.05 < P = 0.10. Data are reported as mean ± SEM. The number of COCs recovered per OPU was greater (P < 0.01) in Senepol (38.8 ± 1.2), Brangus (35.12 ± 3.5), Nelore (33.6 ± 2.3), and Girolando (33.8 ± 1.5) when compared with Gyr (26.5 ± 1.5) and Holstein (16.9 ± 1.6). Additionally, the number of recovered COCs was greater in Gyr (P < 0.01) than in Holstein. Although the number of COCs per OPU was not correlated (P = 0.32) with Day 4 cleavage rates, there was a weak positive correlation (P = 0.03; r = 0.056) between total COCs recovered and Day 7 blastocyst rates. When grouping breeds by species, B. taurus had a greater (P < 0.01) percentage of nonviable oocytes (37.2 ± 0.5%) compared with B. indicus (31.7 ± 0.7%) or cross-bred (33.6 ± 0.7%). The sire (n = 141) used for IVP affected cleavage and blastocyst rates (P < 0.01), but there was no effect of using conventional or sexed semen (P > 0.28). The interaction of breed and season affected blastocyst rates (P < 0.01). During the winter, Holstein donors (41.8 ± 2.8) had greater blastocysts rates compared with Senepol (27.03 ± 2.7), Gyr (28.4 ± 2.7), Brangus (24.2 ± 5.0), and Girolando (30.7 ± 2.7); during the summer, Nelore (34.0 ± 4.0) had greater blastocysts rates compared with Gyr (22.5 ± 2.9), Girolando (23.5 ± 2.5), and Senepol (24.9 ± 1.7). Donor breed was not associated (P = 0.35) with subsequent pregnancy rates following the transfer of fresh IVP (average pregnancy rate = 41.0 ± 1.1). Senepol had antral follicle counts resembling the B. indicus breeds. A breed-by-season interaction highlighted higher efficiency of OPU-IVP in Holstein during the winter and Nelore during the summer. These results add to the current knowledge of the effect of the breed of donor cows on outcomes of OPU-IVP programs.
