Antral follicle count, productive and reproductive parameters in Bos indicus and Bos indicus-taurus prepubertal heifers with early puberty induction

[Contagem de folículos antrais, parâmetros produtivos e reprodutivos em novilhas pré-púberes Bos indicus e Bos indicus-taurus com indução precoce de puberdade]

ABSTRACT

Prepubertal Nelore (G-N = 15) and crossbred Nelore x Aberdeen Angus heifers (G-NA = 15) were used for this study. AFC, live weight, body condition score (BCS), ovary and dominant follicle (DF) diameters were determined in each animal. Puberty induction was performed by insertion of a 4^th use progesterone device (D0) which was removed on D12. Also, 1 mg estradiol benzoate was administered, and estrus intensity was classified (D12). At D21, the presence and diameter of the corpus luteum (CL) were registered. AFC was highly repeatable, regardless of hormone induction in both G-N (r=0.79) and G-NA (r=0.90). The mean AFC was greater in G-N compared to G-NA (24.2±8.5 vs. 17.7±9.0 follicles). A variation in BCS throughout the study occurred in G-NA, but not in G-N. The average weight gain (AWG) was greater in G-NA compared to G-N (0.69±0.33 vs. 0.40±0.29kg/day). The G-NA resulted in a larger diameter of DF at D12 than G-N (11.6±2.7 vs. 9.3±1.5mm). In conclusion, AFC was greater in Nelore heifers, although in both breeds this count was highly repeatable during puberty induction. Crossbred heifers had greater BCS and AWG with greater diameter of DF, indicating higher precocity when compared to Nelore heifers.

Keywords: heifers; puberty; antral follicle count; prepubertal; hormonal protocol