Body growth, testicular biometry and seminal quality of Nelore (Bos Taurus indicus) bulls extensively raised in Middle West of Brazil

Abstract

With the objective to evaluate the morphological testicular characteristics an seminal quality of Nelore bulls raised extensively in a region where predominates the tropical of savannah climate, 271 animals were divided in four age classes: (C 1) of 17 to 20 months; (C2) of 21 to 24 months; (C3) of 25 to 30 months; (C4) of 31 to 36 months and submitted to breeding soundness evaluation (BSE). The animals were weighted immediately before BSE and testicular length (COMP) and width (LARG), as well as the scrotal circumference (CE) were taken. The testicular volume (VT) and testicular weight (PT) were calculated, and seminal quality evaluated through physical characteristics as progressive motility (MOT), vigor (VIG) and gross activity (TUR); morphological characteristics were reported as major defects (DMA), minor (DME) and total (DT). Testicular form (FT) was determined according the reason LARG/COMP, and classified in: long; long moderate; long-oval; oval-spherical and spherical. There was a moderate and positive correlation (P<0,01) between PV and CE, PT and VT. The traits PV, CE, PT and VT showed a moderate and negative (P<0,01) with DMA, DME and DT. The alongated forms of the testicles had predominated, with positive correlation (P<0.01) with
PV, CE and FT. However, the correlation (P<0,05) of PV, CE, FT with spermatic morphology was negative. The spherical format was not present in none of the age class. It was possible to conclude that factors related to testicular biometrics (BT) increase with weight gain in Nelore bulls from 17 to 36 months of age and not only
CE, but VT, PT and FT could also be useful parameters to selection of Nelore bulls.