Antral follicular count does not correlate with ovarian preantral follicular reserve in adult buffalo, Nelore, and crossbreed cattle

Aim of study: To investigate the correlation between antral and preantral ovarian follicular populations in adult cattle, given the discrepant previous reports, and to evaluate this correlation for the first time in buffalo. Area of study: Amazon region, North of Brazil. Material and methods: Ovaries of non-pregnant, adult, cycling, Bubalus bubalis (n=10), Bos indicus (Nelore; n=10), and Bos indicus × Bos taurus (Nelore × Angus crossbreed; n=10) were collected at the slaughterhouse, measured, and weighed. Antral follicles were counted (AFC), and the preantral population was estimated by histology. The correlation between ACF and preantral population was analyzed within each animal group, before and after categorizing females as low or high AFC. Main results: Nelore and crossbreed presented similar ovarian morphometry results (p>0.05), while buffalo (Bubalus bubalis) had the smallest and lightest ovaries (p<0.05). Nelore showed the highest AFC (p<0.05) with buffalo and crossbreed showing similar results (p>0.05). Nelore and buffalo ovaries had similar (p>0.05) amounts of preantral follicles, while crossbreed ovaries had the largest population (p<0.05). A strong indivi-dual variation in the preantral follicular population was observed, and no correlation was observed between AFC and preantral population in any animal group, even after categorizing females as low or high AFC. Research highlights: In cattle, this study brings more evidence about the non-existence of a correlation between AFC and preantral follicular population, and, in buffalo, this is the first report in the literature eva-luating this correlation. These results add to the debate on the use of AFC as a selection method for female reproduction.