Efeito da sazonalidade e da raça sobre a produção de ovócitos, blastocistos e taxa de prenhez em fêmeas bovinas leiteiras

Abstract

In vitro embryo production (IVP) is a reproductive technique that aims to accelerate the genetic gain of herds by multiplying males and females. However, the success of this technique depends on several factors. The aim of this study was to evaluate the effects of animal breed (Gir or Girolando) and time of year (dry period = autumn/winter or rainy period = spring/summer) at the time of follicular aspiration (OPU) on productivity parameters such as: oocyte production, blastocyst production and pregnancy rate of recipients. The database of 1198 OPU, 27135 oocytes and 4483 TEs from the commercial embryo production laboratory, located in Triângulo Mineiro, Minas Gerais, Brazil, was analyzed. The number of viable oocytes and embryos produced was evaluated by ANOVA and the pregnancy rate of the recipients was evaluated by logistic regression, both in the MINITAB program, including in the model the donor's race and season of the year in the OPU, as well as the interactions. There was an effect of the interaction between donor race and time of year in OPU (P<0.01) on the number of oocytes collected and embryos produced. During the rainy season the production of oocytes and embryos was not different for Gir (24.10 ± 0.971; 7.18 ± 0.406 and Girolando (24.54 ± 0.859; 7.50 ± 0.462), however, in the dry season, the Girolando donors (23.58 ± 0.789; 8.85 ± 0.425) had higher production of oocytes and embryos compared to Gir (19.43 ± 0.792; 5.75 ± 0.283). There was no interaction between donor breed and period of the year in the OPU in the pregnancy/ET. However, the period of the year of the transference of the embryos had effect in relation to the pregnancy/ET (49.18 rainy period x 44.13 dry period; P=0.026). donor did not affect pregnancy/ET. In conclusion, donor Girolando produces more viable oocytes and embryos per aspiration in the dry period, and Gir embryos result in higher pregnancy/ET in any period of the year.