Sexual activity and puberty in pure Awassi and crosses and backcrosses with Charollais and Romanov sheep breeds

Abstract

Abstract The aim of this experiment was to study sexual activity, scrotal circumference and the occurrence of puberty in five breed groups of ram lambs. Awassi (A, n = 8), F 1 Charollais‐Awassi (CA, n = 5), backcrossed Awassi‐Charollais‐Awassi (ACA, n = 9), F 1 Romanov‐Awassi (RA, n = 9) and backcrossed Awassi‐Romanov‐Awassi (ARA, n = 8) ram lambs were randomly selected at weaning to be used in this study. Sexual activity was observed weekly by introducing two oestrous ewes into each m ale group for a period of 20 min. At the time of first expressed sexual interest in females, body weights (BW) ( P < 0.05) and scrotal circumferences (SC) ( P < 0.001) differed among ram breed groups, while age and testosterone concentrations were similar. Weights at puberty were similar among the ram breed groups. Puberty, however, occurred earlier ( P < 0.01) in CA, RA and ACA than in A and ARA ram lambs. At puberty, testosterone concentrations were similar while SC were greater ( P < 0.01) in CA, ACA and RA than in ARA ram lambs. However, greater ( P < 0.05) testosterone concentrations were observed in crossbred than in Awassi ram lambs throughout the study. Similarly, BW and SC were greater ( P < 0.05) in CA, RA and ACA than in A and ARA ram lambs throughout the study. Results of the present study indicate that crossbreeding Awassi with Charollais and Romanov sheep breeds improved reproductive parameters in the F 1 crosses and the backcrossed ACAmales compared with the ARA backcrosses and pure Awassi ram lambs. The fact that age differed among ram groups while BW at puberty did not, indicates that body weight is more important than age for puberty occurrence.