Potentialités reproductrices chez les jeunes cailles des blés Coturnix coturnix coturnix

We wished to control the reproductive capacities of European quail, a migratory bird, during the first six months of its Iife. For natural populations, in Europe, this period usually occurs under decreasing daylength and induces inhibition of sexuality. Five groups of European quails, born in August, were reared under a photoperiod which varied from LD 11.20 / 12.40 to LD 15.20 / 8.40, therefore with the same increase in photoperiod, but with the increase starting at different ages:7, 10, 13, 16 and 24 weeks. Molt, fat deposition, corporal weight and genital development were measured regularly. All the birds showed sexual development whatever their age when daylength was increased. However, the speed of sexual development varied between the different groups of birds. Results can be explained by the temporal coincidence between the experimental photoperiodic lengthening and the different mechanisms which underlie the biological cycle of the species. For example, the fall molt normally occurs when the birds are approximately 12 weeks old. In the two first groups of birds this molt was inhibited by photostimulation and the subsequent reproductive development. On the contrary. it occurred in birds in the third group, so daylength started to increase when birds had started to molt. On the other hand, the endogenous cycle of reproduction may enhance sexual development even under short days and may contribute to the highest state of development in the fifth group.