Testicular Development and Puberty in Guzerat Males from Weaning to 36 Months of Age Raised at the Sierra Minera

Abstract

The objectives of this study were to characterize testicular development, assess the existing association between scrotal circumference (SC) and testicular volume (VOL), as well as to identify testicular parameters in puberty of males of the Guzerat breed. Three hundred thirty males were evaluated, totaling 1757 observations every three months, from weaning to 36 months of age. SC, testicular length and width were measured. VOL was calculated according to the method described by Fields et al. Animals with SC ≥ 20 cm were subjected to semen collection through electro-ejaculation stimulation. Animals with at least one motile sperm in the ejaculate were considered as pubertal. The testicular development curve was described using the logistic function, where the maximum inflection point of scrotal circumference and testicular volume was at 13.2 months (18.1 cm) and 23.3 months (389.4 cm3), respectively. The average growth rate of the scrotal perimeter and testicular volume before and after the inflection point was 0.58 cm/m, 16.3 cm3/m, 0.29 cm/m, 7.7 cm3/months of age, respectively. Average age in puberty was 19.6 months, with 250.6 kg of weight, 22.8 cm of scrotal perimeter and 284.7 cm3 of testicular volume. The proportion of pubescent males at 12-16 months was 7.4 %; 41.23 % at 16-20 months; 68 % at 20-24 months; 91.96 % at 24-28 months. At 24 months of age, 91.96 % of the animals were pubescent. A high positive correlation was found between SC and VOL (r = 0.91; P<0.001). These results indicate that, in the Guzeratel race, scrotal circumference efficiently predicts scrotal volume and can therefore be used as a reliable measure for selecting young reproducers.