Effect of season on oocyte quality of buffaloes (Bubalus bubalis): analysis of gene expression and mitochondrial DNA copy number

Abstract

In Brazil, as well as in many other countries, the buffalo herd has been showing rapid growth due economic interests regarding meat and milk production. As seen in other domestic animals, this expansion is supported by the genetic improvement, which in turn depends on several biotechnologies, including the in vitro embryo production. The latter is seen an important tool for enhancing the reproductive efficiency of female buffaloes, however, oocytes used for in vitro embryo production have their quality strongly influenced by environmental factors such as photoperiod, environmental temperature, nutrition among others. Since female buffaloes are seasonally polyestrous, there is a marked reduction in their fertility during the summer in regions of high latitude. However, this environmental effect on buffalo fertility does not appear to be due to a failure on follicular development, but due to an impairment of oocyte developmental competence. The factors determining this impairment are unknown though. Therefore, this project aims to investigate the effect of reproductive seasonality and the number of calving on gene expression (genes related to heat stress, oxidative stress and metabolism) and on the number of mitochondrial DNA copies in oocytes of two buffalo categories, nulliparous and multiparous, collected during the winter and the summer. Oocyte collection will be carried out in Registro/SP, using animals from the Agência Paulista de Tecnologia dos Agronegócios (APTA), because the reproductive seasonality of these female buffaloes has been well characterized. (AU)