BREEDING SOUNDNESS EVALUATION OF TWO AND THREE YEAR OLD NELORE (BOS TAURUS INDICUS) BULLS, RAISED UNDER PASTURE CONDITION

Abstract

Data from 583 Nelore bulls, aging from two and three years old, raised under pasture condition, were used to study andrologic traits (physical aspects: motility and vigor; and morphologic: major and total defects of the semen) and testicular measurements (scrotal circumference - SC and testicular volume - TVOL) to establish a profile of andrologic classification for fertility (BSE). The animals were divided in two groups: young bulls (N = 345), with ages from 18 to 30 months (2 years old), and adult (N = 238), with ages from 31 to 42 months (3 years old). Differences were observed (p < 0.05) for body weight, SC, physical and morphologic characteristics of the semen and TVOL in the two year olds with BSE above and below 60 points. In the three years old bulls differences were observed (p < 0.05) for SC and physical and morphologic characteristics of the semen in bulls with BSE above and below 60 points. The results suggested that body weight and SC affected the reproductive condition of young Nelore bulls. SC and seminal traits were the determining factors in the selection for a better reproductive condition, showing the importance of semen analysis when evaluating bulls raised under pasture conditions.
KEY WORDS: Andrology, breeding soundness evaluation, scrotal circumference, semen, zebu.