Associations between age at puberty, growth traits, plasma IGF-I and leptin concentrations with reproductive performance of Rahmani and Barki male Lambs

The present study aimed to investigate the effect of breed type and puberty status on growth performance, blood IGF-I, leptin concentrations, and the subsequent reproductive performance of Rahmani and Barki male lambs. After weaning at week 14th, two equal groups of Rahmani and Barki male lambs (n = 20 each) were used in the present study till 40 week of age. All lambs followed to tracking the growth traits and puberty development. Blood samples were collected from each lamb every two weeks for IGF-I, leptin, and testosterone examination. Results indicated that Rahmani and Barki lambs had a similar value of growth traits during the experimental period. Also, the average of age at puberty was (37.48 weeks) in Rahmani lambs without significant differences with Barki lambs (36.72 weeks). Besides, the concentration of plasma IGF-I in Barki lambs was higher (P < 0.05) than Rahmani lambs starting from week 26 onwards. However, the concentration of plasma leptin in Rahmani lambs was higher (P < 0.05) than Barki lambs starting from week 28 onwards. Thus, there was a linear increase in plasma testosterone levels during the pre-pubertal up to puberty stage without any significant differences between both breeds. Also, values of semen quality and quantity recorded for lambs of both breeds were almost comparable. Accordingly, the current study results suggest that body mass represented by muscle and fat accumulation were equal for both breeds. These might modify the circulating of IGF-1, and leptin, respectively, exerting an equally positive influence on the reproductive performance of Rahmani and Barki lambs at puberty.