Steroidal feedback on photoperiodic induction of testicular growth and development in two bird species

Present study was performed to demonstrate the effect of exogenous administration of testosterone propionate on photoperiodic induction of testicular growth and development in brahminy myna (Sturnus pagodarum) and baya weaver (Ploceus philippinus). Two groups of brahminy myna and baya weaver (n=5 each) were exposed to 15L:9D (group-I) and 9L:15D (group-II), and received 30 microg of TP bird(-1) for 15 days. Then, the photoperiod was reversed; the one receiving 15L was exposed to 9L and vice versa. Observations on body mass and testis volume were taken at the beginning and at 15 days interval. In brahminy myna, a significant change in body mass occurred under 9L:15D, transfer to 15L:9D, but not under 15L:9D group, transfer to 9L:15D. Also, testes were stimulated under 15L:9D transferred to 9L:15D, but not under 9L:15D transferred to 15L:9D. In baya weaver, body mass increased under 15L:9D and 9L:15D for first 15 days and was maintained until the end of the experiment. Testes enlarged gradually in both groups (15L:9D and 9L:15D transfer to vice versa), but it regressed in 15L:9D group, transferred to 9L:15D after 45 days. Taken together it appears that body mass response indicates the photoperiodic effect and gonadal response indicates the hormonal effect. Finally results conclude that the photoperiod and circulating testosterone levels feedback on to hypothalamus regulates reproductive cycle in these birds.