Dinâmica hormonal e taxa de embriões in vitro de fêmeas bovinas previamente tratadas com somatotropina recombinante bovina (rbST)

Abstract

The use of rbST before to the initiation of follicular puncture sessions may be a valuable resource for increasing the number and quality of oocytes collected in vivo and embryos produced in vitro. To evaluate the effect of pre-treatment of bovine recombinant somatotropin (brST) on the in vitro production of embryos and the hormonal dynamics of progesterone, estradiol, growth hormone and IGF-1 of bovine females. Twelve animals were divided into three experimental groups: control (n = 4), 250mg (n = 4) and 500mg (n = 4) of rbST. Ovum Pick-Up (OPU) was performed at 7-day intervals. The cumulusoocyte complexes (COCs) were classified under a stereomicroscopic magnifying glass. Blood samples (plasma) occurred 60 days before the first aspiration, at intervals of 12 days, with collections performed on the same days as the rbST applications. The in vitro maturation period (IVM) was 24h. Subsequently, the COCs and spermatozoa were incubated for 22h. After in vitro fertilization (IVF), the development of blastocysts was evaluated seven days after the initiation of IVF (D0). Hormonal dosages were performed using commercial kits according to the manufacturer's recommendations. The data for the variables were submitted to the normality test, the analysis of variance (ANOVA) or the non - parametric Wilcoxon test for comparison of means, in the probability of 5%. The hormonal plasma concentrations were submitted to the Cramer-von Mises Normal Test and the Student-Newman-Keuls (SNK) mean score was 5% of probability. Qualitative data were compared by the chi-square test, for p<0,05. The analyzes were performed using the Statistical Analysis System (SAS Institute Inc, 2015). The pre-treatment of bovine recombinant somatotropin (brST) in Girolando cattle did not influence the rate of embryonic development in in vitro production, nor did it have an effect on the hormonal dynamics of bovine females in plasma concentrations of progesterone, estradiol and IGF -1 when between the groups treated with 250 mg and 500 mg and the untreated group, there was also no significant variance between the days of application and OPUs.