Twenty three 10-months-old Nellore bulls, raised under pasture conditions in Brazil, were used to study puberty. Monthly measurement of scrotal circumference and testicular width and length were recorded. Semen was collected by eletroejaculation and evaluated according to physical and morphological aspects. Penile and prepuce detachment percentages were also evaluated. The ages of the presence of first spermatozoa in the ejaculate (ISEM1), first motile spermatozoa in the ejaculate (ISEM2), seminal puberty (IDPUB) and detachment between penile and prepuce (IDPPRE) were calculated. Scores of breeding soundness were measured. ISEM1, ISEM2, IDPUB and IDPPRE were 13.1±2.2, 13.6±2.3, 14.8±1.8 and 18.1±1.9 months, respectively. At 16 months of age, the animals presented 91.4%, 82.6% and 73.9% with ISEM1, ISEM2 and IDPUB reached, respectively. High positive correlation were observed between age and corporal and testicular growth or seminal physical aspects. Negative correlation was verified between age and spermatic defects. High negative correlation was observed between age and score of scrotal circumference at puberty (-0.7;7 P<0.001). Precocious puberty was observed before 15 months of age. From ISEM1 to IDPUB, 51 days were elapsed. Young bulls with larger testicles reached puberty earlier.
beef cattle; puberty; Nellore; testis; sperm; scrotal circumference
