Dimensões do trato reprodutivo e relação com fertilidade em fêmeas bovinas

Abstract

Ovarian follicular development and external morphometry are characteristics of easy access to classify cow groups phenotipically. Cows and heifers may be grouped according to their ovarian antral follicle count (AFC) and external traits in an attempt to predict their fertility and to establish early reproductive culling priority. This study focus on relating morphometric characteristics of the reproductive tract to the AFC and cumulus oophorus oocyte complex (COC) yield. In experiment I, the genital tracts of 360 abattoir Zebu/Holstein crossbred cows were used. Length and width of the rima vulvae, cervix, uterine horns, oviducts and ovaries were measured. Ovarian antral follicles were counted, aspirated and COC counted and classified (1- excellent to 5- degenerate). For statistical analyses, based on frequency distribution, three ovarian size and rima vulvae length and width classes were established. An index of COC quality (CQI) was established which weighed overall gamete quality per individual cow (1-low to 5 high). In experiment II, the same external measurements were performed on live Tabapuã breed cows (n=80) and internal reproductive tract measures were taken by ultrasound. Rima measurements were divided by the cow weight in order to consider a relative to size instead of a direct measure would be considered for analyses. For small, medium and large rima length, respectively, mean number of COCs were 10.27, 12.55 and 14.85 (P=0.12), and AFC were 42.63, 40.18 and 48.03 (P=0.25). Large rima width class CFA was greater (3.50, P= 0.0004) than in the small (2.57) and medium (2.45) classes. COC counts did not differ between rima width classes. Larger ovaries had greater (P=0.001) AFC than smaller ovaries (33.16, 42.35 and 48.62 for the small, medium and large ovarian classes, respectively). In experiment 2, AFC was greater for the longer relative rima length and width (18.96 and 20.08; P=0.035) compared to the shorter relative length and width (14.76 and 11.16; P=0.0001). In conclusion, it was more accurate to predict ovarian reserve when the genitalia measurements were relativized to the size of the animal. This approach proved useful and relatively easy to be applied in the selection of cows with higher antral follicle counts under field conditions in the conditions of the present experiments.