LIGHTING PROGRAMS FOR BROILERS THAT REDUCE LEG PROBLEMS WITHOUT LOSS OF PERFORMANCE OR YIELD

This study tested the effects of light schedules on performance and yi elds of broiler chickens. In Experiment 1, light treatments during Day s 1 to 49 of age were: 1) 23 h light (L): 1 h dark (D); 2) 16L:8D;3) 1 6L: 3D:1L:4D; and 4) 16L:2D:1L:2D:1L:2D. In Experiment 2, Light Treatm ents 1 and 2 were the same as Treatments 1 and 4, respectively, in Exp eriment 1; 3) 23L:1D Days 1 to 7, 16L:8D Days 8 to 14, the light perio d was increased by 2 h/wk during Days 15 to 35, and 23L:1D Days 36 to 42; and 4) 23L:1D Days 1 to 7, 16L:8D Days 8 to 14, 16L:3D: 2L:3D Days 15 to 21, 16L:2D:4L:2D Days 22 to 28, 16L: 1D:6L:1D Days 29 to 35, an d 23L:1D thereafter. In Experiment 1, BW was greater in Treatment 4 th an Treatment 2 at 22 (708 vs 642 g) and 49 d (2,948 vs 2,797 g), perce ntage leg problems was lower in Treatments 2 to 4 (9, 10, and 6%, resp ectively) than in Treatment 1 (20%), and percentage Grade A was greate r in Treatment 4 than Treatment 2 (60 vs 46%) at 49 d. In Experiment 2 , BW was greater in Treatment 1 (692 g) than Treatments 3 (617 g) and 4 (620 g) at 21 d, and the incidence of tibial dyschondroplasia was lo wer in Treatment 2 (3.1%) than Treatment 3 (15.3%) at 42 d. There were no differences for mortality among treatments in either experiment.