Study of oocyte and embryonic quality of super precocious heifers (Bos indicus) aspirated prior to the breeding season in the municipality of Vilhena – RO, Brazil

Reproductive efficiency in females plays a fundamental role in the economic sustainability of beef cattle herds, mainly in characteristics related to the sexual precocity of heifers, with the increasing use of in vitro production (IVP) of embryos. The present study aimed to evaluate the quality of oocytes and embryos produced from Nelore heifers aged 11 and 12 months submitted to the precocity challenge, aspirated prior to the breeding season. The study was conducted in the months of September and October 2023, on a farm located in the municipality of Vilhena-RO. The animals were subjected to a pasture regime predominantly formed by Brachiaria and received protein supplementation with consumption of 0.6% of live weight added with Miyagi grass silage. Follicular aspirations took place in the morning, with the aim of not negatively influencing the ambient temperature. To conduct the research, 23 animals that underwent the follicular aspiration process were used. Subsequently, the oocytes were sent to the laboratory for selection, maturation, and fertilization. In the laboratory, these oocytes were selected to classify the viable ones and fertilize them. In total, 562 viable oocytes were collected, which converted into 129 embryos suitable for transfer. Oocyte conversion was 22.9%, a relatively considerable number compared to the conversion of adult matrices. It is evident, therefore, that follicular aspiration of super early heifers can be used in genetic improvement programs since the oocyte quality of these animals makes the process of genetic gain and generational advancement viable.