Changes in body weight, semen characteristics and fertility in 20 seven-month-old fertile roosters belonging to Fars Center for the Study of Native Chicken were studied at 15-day intervals from 15 Ordibehesht (May 2001) to 15 Azar 1380 (November 2001). Using the abdominal massage technique collected semen. The roosters were slaughtered at the end of the experiment and their testes were weighed. Semen volume, semen pH, and sperm motility were greater in autumn than in spring and summer ((P<0.001). Maximal sperm concentration was found in spring and autumn while the minimum occurred in summer (P<0.001). Total number of live and normal sperms was also highest in autumn. Mean live body weight, combined testes weight, semen volume, total number of live-normal sperm, and the percent fertility as well as hatchability of eggs sired by roosters were significantly greater for the heavy roosters (mean initial body weight of 2541 g) than the light (mean initial body weight of 2085 g) ones (P<0.05). Testis weight as a percentage of live weight was not significantly different between the heavy and light roosters (P>0.05). Body weight did not significantly affect the other trait measurements (P>0.05). In conclusion, as far as semen characteristics are concerned, it is suggested to breed chickens during the cooler months, and use heavier roosters for breeding purposes.
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