Termination of LH secretion in Japanese quail due to high- and low-temperature cycles and short daily photoperiods

Mature male Japanese quail were transferred from 16L:8D (19°) to one of the following combinations of daily light-dark and temperature cycles, 8L:16D (12 hr, 19°:12 hr, 9°), 12L:12D (12 hr, 19°:12 hr, 9°) and 12L:12D (16 hr, 19°:8 hr, 9°). The low temperature is for the middle of the dark period in each treatment. In the control groups, birds were transferred to the same photoperiodic conditions as the experimental groups, but without changes in ambient temperature. Blood samples were collected every other day for 30 days and circulating levels of plasma LH were estimated by radioimmunoassay. Both the change in conditions from 16L:8D to 8L:16D with the temperature lowered for 12 hr and that from 16L:8D to 12L:12D with temperatures lowered in one case for 12 hr and in the other for 8 hr caused a lowering in plasma LH levels in all the birds to reproductively quiescent levels. The cloacal protrusion of all these birds regressed completely. In control groups, however, most if not all the birds remained in active breeding states although the levels of circulating LH decreased to basal breeding levels of 1–2 ng/ml. The results indicated that in addition to a change from long to short days an alternation of high and low temperatures was sufficient supplementary information in causing termination of LH secretion and inducing regression of the gonads and the accessory sex organs in this species.