Maturao sexual e parmetros reprodutivos em touros da raa Nelore criados em sistema extensivo

Abstract

The objective of this study was to verify the stage of sexual maturity, occurrence of the testicular format and the relationship among reproductive characteristics. Data were used from 5903 Nellore bulls averaging 21 months submitted to the soundness evaluation from 1999 to 2003. At the time of the evaluation, the following characteristics were recorded: scrotal circumference at soundness evaluation (31.99 ± 2.23 cm), left testicular length (11.21 ± 0.98 cm) and right testicular length (11.26 ± 0.97 cm), left testicular width (5.92 ± 0.44 cm) and right testicular width (5.97 ± 0.46 cm), testicular format (1.72 ± 0.46), testicular volume (632.21 ± 132.72 cm3), individual motility (69.56 ± 12.31%), vigor (2.87 ± 0.61), as well as total defects (22.19 ± 11.13%) and major defects (15.86 ± 10.45%) of the spermatozoa. The frequencies of the testicular formats were long (30.80%), long-moderate (66.19%), long-oval (2.49%), oval-spherical (0.02%) and spherical (0.04%). Correlations between the scrotal circumference and the reproductive traits were positive. Scrotal circumference is a good trait for selection of young Nellore bulls. More than 70% of the animals studied are sexually mature at 21 months old.