Cattle breed affects in vitro embryo production in a large-scale commercial program on dairy farms

Sexed cryopreserved semen is widely used in vitro embryo production (IVEP) for cattle reproduction in Brazil. However, differences between donor breeds regarding variables related to the IVEP process have been reported. This study aimed to evaluate factors affecting the efficiency of IVEP using donors of different genotypes and sexed sperm from Gir and Holstein bulls in a commercial program of IVEP. Higher oocyte and blastocyst means per OPU session were observed in 1/2 HolsteinxGir donors. Gir donors showed higher percentage of blastocyst than Holstein donors, with blastocyst production of crossbreed donors being similar to the other breeds. Moreover, embryos in the stage of expanded blastocyst and hatching blastocyst had a higher capacity of resulting in pregnancy than embryos in the blastocyst stage. In relation to the crosses of the donor and the bull used, no effect was found on the percentage of blastocyst and pregnancy. However, donors with greater number of oocytes recovered had a higher number of blastocysts and pregnancies per OPU session. Finally, OPU sessions performed with 21-day intervals for two years did not affect the pe rformance of Gir donors on IVEP. Thus, the conclusion is that donor breed influences the rate of oocyte retrieval. Moreover, embryo production is affected by donor breed and the number of viable oocytes recovered. Only embryo developmental stage influences the pregnancy rate. Finally, bull breed does not affect IVEP results and there was no effect of repeated OPU sessions on Gir donors in these variables. These results provide new insights related to IVEP in large scale.