Photoperiod and thermal effects on the productive and reproductive performance of Ross Tented egg-type and Hubbard broiler chicks living under subtropical conditions.

Abstract

In egg-type pullets, the body weight was significantly higher under constant 20 L:4 D and 10 L:14 D up their 72nd day of age (d), followed by 20 L:4 D, than in the control (10 L:14 D). The latter variant positively affected the liveweight gain and earlier sexual maturity. Constant 20 L:4 D also increased earlier sexual maturity, plasma corticoid content of the blood, and egg number significantly over the control. Egg number was also ensured and stimulated by 10 L:14 D up to the 72nd d and their 20 L:4 D. In the treatment 20 L:4 D changed to 10 L:14 D maturity and egg number decreased significantly. Reduction of the 20 L:4 D d in steps of 2 h/week to 10 L:14 D on the 49th day resulted in a significant increase in egg number and liveweight. Reversing this light regime reduced both features. Under elevated temperature (3 to 5 K above normal) this reduction was postponed to the 11th d and following. The elevated temperature increased significantly the carcass traits, except the flack, neck, and abdominal fat. The combination of the light and temperature regime did not yield any significant differences for the carcass weight at conventional temperatures and for the body weight.