| Summary: | <span>The objective of this study was to evaluate the effect of the breed of the oocyte donor cow and bull (Holstein versus Gyr) on in vitro production (IVP) parameters of bovine embryos comparing the mean number of recovered oocytes and oocytes suitable for culture, the rate of suitable oocytes, and cleavage and blastocyst rates. Data from 1,000 follicular aspiration sessions (OPU), including 500 in donor cows of the Holstein breed and 500 of the Gyr breed, were collected. The results were analyzed by the unpaired Student t-test and chi-square test, adopting a level of significance of 5%. The mean number and standard deviation of recovered oocytes and oocytes suitable for culture were 15.1±13.0 and 8.7±7.6 for the Holstein breed and 15.5±11.9 and 9.1±7.9 for the Gyr breed. The rates of suitable oocytes were 57.7% and 58.5% for Holstein and Gyr breeds, respectively. A significant difference between breeds was observed for the number of oocytes suitable for culture (P<0.05), but not for the number of recovered oocytes or rates of suitable oocytes (P>0.05). Similarly, the breed of the oocyte donor cow and bull influenced cleavage and blastocyst rates (P<0.05). The cleavage rates were 65.7, 60.3, 59.6 and 56.5% for the combinations (donor breed x bull breed) Holstein x Holstein (G1), Holstein x Gyr (G2), Gyr x Holstein (G3) and Gyr x Gyr (G4), respectively, with G1>G2, G1>G3, G1>G4, G2=G3, G2>G4, and G3>G4. The blastocyst rates were 28.1, 33.3, 26.8 and 31.0%, respectively, with G1>G2, G1=G3, G1<G4, G2<G3, G2=G4, and G3<G4. It can be concluded that the breed of the donor cow and bull influenced IVP parameters, with a larger number of oocytes suitable for culture in the Gyr breed.</span>
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