The levels of LH and T increased sharply after turkeys were switched from SD to LD at 29 wk of age. These photostimulated increases in LH and T were maintained for about 4 wk, then gradually declined until 35 wk of age, the latest age examined in the present trials. In male turkeys switched from SD to LD, the response in LH has previously been reported to be very rapid. In turkey hens, an increase of LH level after photostimulation is also rapid, occurring during the first scotophase after the first LD photophase. Buy Advair Diskus Online
Photostimulation also stimulated an increase in testis growth resulting in the higher testis weight in the SL group in comparison to the LL group at 35 wk of age, which was 6 wk after photostimulation. However, no associated increase in semen production was observed during the 6 wk after photostimulation, even though the spermatogenesis from spermatogonia to spermatozoa is short in male birds; in Japanese quail this requires only 11 days. The response to photostimulation in turkey hens is different. Good egg production is induced within about 3 wk when turkey hens are switched to an LD photoperiod from an SD photoperiod. Compared to the relatively low-amplitude increases in plasma LH and T levels occurring at about 18 wk of age, increases in plasma LH and T levels induced by LD photostimulation at 29 wk were both rapid and of relatively high amplitude. The mechanism of quick response to photostimulation is possibly due to rapid increase in GnRH secretion. Rapid increase in GnRH is observed within 23 h after a single LD photostimulation in quail.