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Beef donor cows with high number of retrieved COC produce more in vitro embryos compared to cows with low number of COC after repeated ovum pick-up sessions

Autores
F.M. Monteiro, E.O.S. Batista, L.M. Vieira, B.M. Bayeux, M. Accorsi, S.P. Campanholi, E.A.R. Dias, A.H. Souza, P.S. Baruselli

Resumo

The aim of the present study was to evaluate whether repeated ovum pick up (OPU) procedures may affect the efficiency of OPU programs for in vitro embryo production (IVEP) in Bos indicus (Nelore) donors. In addition, the repeatability (r) efficiency of IVEP was also assessed. Data available were from 432 OPU-IVEP sessions that were performed at random stages of the estrous cycle in 36 cycling, non-lactating Nelore donors. Semen from three Nelore bulls was used for the in vitro fertilization (IVF). Donors were submitted to 12 consecutive OPU procedures, with an interval of approximately 30 d between sessions. Data were analyzed as repeated measures using the GLIMMIX procedure of SAS 9.3. Cows yielding ≥ 15 COCs were defined as “High” COCs, and cows with <15 COCs were defined as “Low” COCs donors. The number of COCs retrieved decreased over time in donors classified with High COCs and remained fairly steady in cows with Low COCs at the beginning of the program (Psession*COC retrived goups = 0.02). Moreover, the number of COCs retrieved (P < 0.0001), and number of blastocysts produced per OPU (P = 0.001) was greater for the High COCs donors compared to the Low COCs category, and these results were consistent across OPU sessions. Interestingly, there was no effect of COCs category on the rate of blastocyst development (P = 0.83). In addition, number of blastocysts produced were not affected by repeated OPU (P = 0.37) and interactions between time and COC category (P = 0.72). Similarly, blastocyst rate was not affected by repeated OPU (P = 0.21) and interactions between time and COC category (P = 0.58). Despite of COC category of the donor cows, repeatability was high for the number of COCs retrieved (r = 0.81), number of blastocysts produced per OPU (r = 0.79), and blastocyst rate (0.69). In conclusion, overall numbers of COCs decreased over time in donors classified as having high COCs. However, cumulative amounts of produced blastocysts were greater in donors with high COCs. More importantly, high repeatability was observed in terms of IVEP efficiency. Therefore, IVEP programs can be significantly improved with more aggressive selection towards donors with greater numbers of COCs.

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