CONICET | Buscador de Institutos y Recursos Humanos

One of the parameters that has the most influence on in vitro embryo production programs is the number of oocytes obtained in each follicular aspiration session (ovum pickup; OPU). A significant impact of the breed of the donor on this parameter has been reported. The objective of this work was to compare the parameters of an in vitro embryo production program of cows of different breeds in Paraguay. A total of 4811 OPU sessions were performed between 2016 and 2019 in cows classified according to breed and type. Beef-type breeds: Nelore (Bos indicus): n = 1569; Aberdeen Angus (Bos taurus): n = 1276; and Brangus (Cross): n = 182 OPU, and Gyr (Bos indicus): n = 1086; dairy breeds: Holstein (Bos taurus): n = 401, and Girolando (Cross): n = 297. The oocytes were aspirated and transported to the same laboratory located in Asunción, Paraguay. The in vitro embryo production protocol was similar in all types. Bull semen tested for IVF was used. The number of oocytes, percentage viability, and percentage embryo production were evaluated. Additionally, the mean and standard deviation of the variables were calculated to show the efficiency of the processes, according to the production aptitude of the donors (meat or milk) and the breed type (Bos indicus, Bos taurus, or crosses). Continuous data were analysed with ANOVA and Tukey?s post hoc comparisons. Categorical data were analysed using Chi-squared at a significance level of 0.05. In this work, the production aptitude had no significant effect over the studied variables. However, some significant differences were found considering the breed type of the oocyte donor cow, as shown in Table 1. When crosses with the pure breeds are compared with their crosses, we found that Brangus produced more pregnancies and a greater number of oocytes/OPU compared with Angus (P

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