Impact of phase-feeding on the growth performance of broilers subjected to high environmental temperatures

Experiments were conducted to evaluate the effects of phase feeding (PF) on broilers subjected to heat stress during the grower and finisher periods. Birds were fed diets containing lysine, sulfur amino acid (SAA), or threonine levels based on NRC (1994) recommendations or predictions from linear regression equations (PF). With PF, diets were switched every other day, resulting in steadily decreasing lysine, SAA, and threonine levels. In Experiment 1 (42 to 56 d), growth performance was unaffected (P > 0.05) by diet, and cost per kilogram of weight gain did not differ (P > 0.05) between treatments. In Experiments 2 (23 to 42 d) and 3 (42 to 63 d) birds were housed in environmental chambers and subjected to high (15 h at 35 C, 9 h at 23.9 C) or normal (23.9 C) temperatures. In both experiments, heat stress reduced (P < 0.05) growth performance and increased (P < 0.05) percentage leg yield. Moreover, heat stress decreased percentage breast yield (P < 0.05) in Experiment 2. Growth performance and carcass yield were unaffected (P > 0.05) by PF relative to birds fed NRC-based diets, with the exception of feed efficiency, which was reduced (P < 0.05) by PF under normal temperatures in Experiment 2. Data indicated that dietary lysine, SAA, and threonine levels may be reduced every other day under a PF program without adversely affecting growth performance or carcass yield of birds exposed to high environmental temperatures. Cost analysis indicated that savings might be available with PF under high temperature conditions.