Prediction of postpubertal reproductive potential according to prepubertal body weight, testicular size, and testosterone concentration using multiple regression analysis in Kivircik ram lambs

The relationship between the prepubertal body weight, testicular size, testosterone concentration, and postpubertal reproductive function was investigated in Kivircik ram lambs. The body weight, testicular size, and testosterone concentration were measured every 20 days between 60 and 420 days of age. Semen was collected from the ram lambs at 7, 8, 9, 10, 11, 12, 13 and 14 months of age. Data obtained were analyzed by best subsets regression model. We determined that body weight, scrotal circumference, testicular length, and testosterone levels in the early prepubertal period (days 80, 100, and 120), when combined with each other, allow the determination of the postpubertal (days 220, 240, 260 and 280) testicular diameter. Body weight and testosterone at prepubertal ages, either alone or in combination with other variables, were related to semen volume at postpubertal ages (at 7, 8, 9, 11, and 14 months of age). It is concluded that there is a significant relation between postpubertal reproduction characteristics and the selection of Kivircik ram lambs during the prepubertal period (especially between days 80 and 120) according to body weight, testicular characteristics, and testosterone hormone concentrations. According to the relationship among these characteristics, selection of ram lambs at juvenile ages will improve the effectiveness of the selection and then the economic gain of sheep-breeding operation