Determinants of puberty and age of sexual maturity in Nigerian indigenous breeds of male goats

Abstract

This study was conducted to ascertain the pubertal and sexual maturity characteristics of Nigerian native goat breeds. The research was carried out on three goat breeds; Sahel (SG), Red Sokoto (RSG), and West African Dwarf (WAD) goats. Each breed was represented by eight (8) animals (n=24) and housed in separate pens based on breed type. All bucks were weighed at birth and bi-weekly using digital weighing scales until they reached puberty. Scrotal circumference measurements were taken every two weeks until the end of the study. Semen was collected immediately after preputial separation and all semen samples were labelled and placed in a thermo-flask immediately and subsequently transported to the laboratory for evaluation. The mass motility and the forward motilities of the spermatozoa were observed using a light microscope. The percentage of live, dead, and abnormal sperms were determined after staining with eosin and negrosin stains. The sperm cell concentration was determined by counting spermatozoa with a hemocytometer. Result obtained indicate that at the 14th and 16th weeks of age, the mean scrotal circumference of bucks ranged from 5.14±0.66 cm to 7.06±0.71 cm, 6.32±0.29 cm to 8.05±0.42 cm, and 5.50±0.74 cm to 7.06±0.71 cm in SG, RSG, and WAD bucks, respectively. Puberty in Red Sokoto bucks was achieved at an average age of 14 weeks, with a mean sperm concentration of (116.17±28.47 x 106), progressive sperm motility of (65.00±9.92%), and a mean body weight of 10.17±1.26 kg. Sahelian and WAD bucks reached puberty at the 16th weeks, with sperm concentrations of 106.29±25.18 x 106 and 107.60±19.99 x 106, mean sperm motility of 65.00±9.94% and 76.00±4.8%, and mean body weights of 11.29±1.59 kg and 7.78±0.70 kg, respectively. To summarise, this study revealed that breed, age, scrotal circumference and body weight at puberty played significant roles in determining sperm characteristics and sexual maturity.