Refractoriness in quail leads to a reduction in the photoperiodic drive on LH secretion.

The hypothesis was advanced that the long-day castration response in quail should become less pronounced in birds made refractory by exposure to long photoperiods. This was tested by pretreating two groups of castrated quail with testosterone for 9 weeks to suppress LH secretion whilst exposing them either to short days or to long days. The castration response was then measured on long days by withdrawing the testosterone and following the subsequent rate of increase in LH secretion. In both groups LH concentrations increased steadily for 7 weeks after removing the testosterone but the rate of increase in the group previously exposed to long days was only 50% of that in the group previously held on short days (P less than 0.025). The long-day castration response in quail not pretreated with testosterone was not altered by retaining the birds for 9 weeks on short days before transfer to long days.