Productive Performance and Carcass Characteristics of Broiler Chickens Fed on Diets with Different Protein, Energy Levels, and Essential Oils During the Warm Season in Dry Tropics

This study evaluated the productive performance and carcass traits of broiler chickens during the warm season in dry tropical conditions. Two hundred, 1-day-old chicks were used. Birds were fed on reduced (RED) and standard (STD) diets, and two essential oils (EOs) levels, 0 and 200 ppm. The RED diets were formulated with 10% less energy and 10% less protein than STD diets. In the starter phase, weight gain was greater (<i>p</i> < 0.01) in birds fed STD than birds fed RED. In the starter phase, productive variables were not affected (<i>p</i> ≥ 0.14) by EOs. In the finisher phase, greater feed intake (<i>p</i> = 0.02) and higher weight gain (<i>p</i> = 0.04) were observed in chickens on STD. Feed conversion ratio was similar (<i>p</i> = 0.97) for STD and RED. Throughout this study (1-42 d), greater feed intake (<i>p</i> = 0.02) and higher weight gain (<i>p</i> < 0.01) were found in chickens on STD. Feed conversion ratio was similar (<i>p</i> = 0.51) for STD and RED. Broiler chickens on EO-supplemented diets had better feed conversion (<i>p</i> ≥ 0.08). Hot carcass weight was greater (<i>p</i> < 0.01) in birds on STD. Greater yields of leg-thigh (<i>p</i> = 0.01), back (<i>p</i> = 0.01), and wings (<i>p</i> < 0.01) were observed in RED. Carcass yields, breast yield, pH, and meat temperature were not influenced (<i>p</i> ≥ 0.14) by nutrient concentrations in the diet. Carcass evaluations were not affected (<i>p</i> ≥ 0.11) by EOs. Body temperature was lower (<i>p</i> = 0.03) in birds receiving RED, however EOs had no effect (<i>p</i> ≥ 0.22) on body temperature. For the length of the study, at 20:00 h, broiler chickens fed on RED diets showed lower (<i>p</i> = 0.04) body temperatures. In conclusion, broiler chickens were under heat stress during the study, and body temperatures were reduced in chickens fed on RED diets or with EOs. Diet modification or EO-supplementation may improve feed conversion, though RED diets may have a negative effect on weight gain or carcass values.