Dinâmica folicular ovariana e padrão hormonal das éguas do grupamento genético “baixadeiro”

Abstract

The study aimed to evaluate the reproductive seasonality through pre follicular development and post-ovulatory and progesterone concentration in the dry and rainy seasons. The mares (n = 14) were synchronized with two spaced doses of PGF2a. had weight and BSC followed during the trial period. They were evaluated by ultrasonography every other day for registration of follicular development, as well as data and uterine tone morphoechogenicity. This evaluation became daily when presented follicles > 30mm. To test the hormonal nine mares were used, collecting blood into heparinized tubes on alternate days beginning 72h after synchronization and extending to 10 days after ovulation. Climatic data for the period were also analyzed. For the 14 mares, there was no statistical difference (p> 0,05) for synchronization, weight and BSC between the rainy and dry seasons, as well as no significant difference in ovulation rate and the characteristics of follicular development, except for medium and large follicles which were higher in the rainy season and dry, respectively. Hormone test, there was no statistical difference for ovulation rate. Progesterone concentrations were <1 ng / ml prior to ovulation and increasing until it reaches values between 8 and 13 ng / mL in the dry and rainy seasons, respectively. In the pre-ovulatory phase was recorded small, medium and large follicles when progesterone concentrations were <1 ng / ml, while in the post-ovulatory phase were identified only small and medium follicles under high concentration of progesterone. Mares with ovulation not had a mean concentration of progesterone <1 ng / mL during the two periods. There was statistical difference hour light / day but not for rainfall, although most ovulations occurred during the rainy season. Although there is difference in concentration between the periods it can’t be considered a reproductive seasonality for these animals. The absence of ovulation is related to weight loss and poor body condition, maintaining levels below 1 ng / ml and conditions characterized nutritional anoestrus. Thus, it can be concluded that the environmental conditions typical of Maranhão Lowlands, the mares of the grouping Genetic Baixadeiro showed no reproductive seasonality, even if there is difference hour light / day between periods. They are cyclically throughout the year, since nutritional factors allow maintenance of weight and body condition.