The objective of this study was to investigate the effect of photoperiod on histomorphological changes in testes and bursa, immune function parameters like total leukocyte count and lymphocyte count and serum testosterone level of guinea fowl (Numida meleagris) during different breeding seasons. Bursa and testes were collected from 10 mature male guinea fowls aged 6-8 months during full breeding (summer), low breeding (autumn) and non-breeding (winter) seasons (n=10). Tissues were stained with H&E and Image J^® software was used for histometric analysis. Statistical analysis revealed that breeding seasons affected significantly (P<0.01) all morphological parameters of testes and bursa. The parameters of testes were found significantly higher during full breeding season which decreased significantly during non-breeding season through low breeding season. A similar trend was shown by diameter of testicular seminiferous tubules. However, the parameters of bursa showed highly significant (P<0.01) value during non-breeding season but this value declined non-significantly (P>0.05) during low breeding and full breeding seasons. Immune parameters exhibited a significantly higher value during non-breeding season with a significantly declining trend during low breeding and full breeding seasons. Serum testosterone levels were also significantly (P<0.01) different during all breeding seasons. Testosterone showed a negative correlation (r =-0.946) with immune function parameters. It is conceivable that increased steroid hormone synthesis enhances testicular activity during full breeding season but depresses the immune function. This trend however, reversed in non-breeding season, which assists the survival in the hard climatic conditions.

Key words: Guinea fowl, Histomorphology, Immune function, Seasons, Testis, Testosterone profile