Abstract
The present work was conducted to elucidate the relationships between chronological age, testosterone concentration and testis size of Najdi and Naemi ram lambs under desert conditions to determine the reproductive capacity of the above two breeds. The postnatal development of the seminiferous epithelium of the testes was also monitored. A total of 90 (45 Najdi and 45 Naemi lambs) aged between one and nine months, with five lambs at each month of age for each breed were used. The results showed that the testosterone concentration increased dramatically and rapidly between five and six months, followed by a period of gradual growth where testicular size was increased from 3 to 6 months of age. There was a significant (P < 0.05) difference in testosterone concentration (TC) and testis size (TS) in ram lambs between different age groups, similarly there were significant differences between body weights and lamb age between one and nine months. A positive correlation between the increasing body weight and the size of the testicle was observed. The testicles of lambs at each age-group had a different histological appearance except those of Najdi lambs at 2, 3 and 4 months and Naemi lambs at 2, 3, 4 and 5 months, where few differences were apparent. Small quantities were of spermatozoa appeared at the eighth month of age and increased in the ninth month. In conclusion, the current findings indicate that puberty in Najdi and Naemi rams occurs at the 8th and 9th month of age, respectively.