A total number of 92 cockerels aged 30 weeks (46 Nana and 46 nana) were randomly distributed into two groups. Each group within each genotype had fed a diet containing 14 or 16% crude protein (23 each). The experimental period was run from 30 till 40 weeks of age. Results obtained could be summarized as follows: - The daily feed intake was significantly differed according to genotype and dietary protein level. The interaction (G*T) being also highly significant. - The body weight of cocks did not significantly affected by genotype throughout the study. - The low protein diet significantly increased body weight of cocks at 40 weeks of age compared to high protein diet. - The Nana cocks gene had significantly higher semen volume than that of normally feathered one. The cocks fed high protein diet have significantly higher semen volume than that of cocks fed low protein diet at 32 weeks of age. However, the effect of dietary protein level on semen volume at 36 and 40 weeks of age did not significant. - The naked neck gene and dietary protein diet did not significantly affected on total plasma protein at 32 weeks of age. - In conclusion, the low protein diet may improved the semen characteristics of heterozygous naked neck cocks under low ambient temperature.