Abstract
The present study was conducted to evaluate the annual changes in reproductive ability in male Guinea fowls (180-571 days old) under natural photoperiod. The semen vol., sperm concentration, copulatory organ size and plasma concentration of testosterone (T) were measured throughout the year.
1. The copulatory organ continued to grow gradually till early September, then after regression in molting period, it grew again and kept the full maturity size even after December. The copulatory organ size does not correlate neither day length, air temp, nor plasma T concentration.
2. The semen vol. and sperm concentration began to increase from April and maintained high values between late May and early October (semen vol.: 9-38 μl, sperm concentration: 6.51×108-29.9×108/ml). While the values decreased remarkably in the late molting period and January to February.
3. The variations in plasma T concentrations were well corresponded with the changes of natural day length, and the maximum (2.95±0.81ng/ml) and minimum (0.12±0.02ng/ ml) values were observed in early July and late September when they began to molt, respectively. The mean plasma T concentrations during the periods of breeding, non-breeding and molting were 1.25±0.12ng/ml, 0.64±0.05ng/ml and 0.20±0.05ng/ml with significant difference (P<0.01) among each value.
4. The coefficient of correlation between day length, air temp., plasma T concentration and each measurement item were summarized in Table 1.
