Effect, of different dietary protein levels supplemented with limiting amino acids on the performance of broilers in extreme summer.

Abstract

One hundred twenty day-old straight run broiler chicks were divided into 3 groups with four replicates in each group and fed three different levels of protein i. e. 23% and 21%, 21% and 19%, and 19% and 17% in starting and finishing periods with fixed levels of limiting amino acids viz. lysine (1.25 and 1.16%), methionine (0.55 and 0.50%), threonine (0.95 and 0.88% in starting and finishing period respectively). The temperature in house during the experimental period was recorded as minimum 28.9 to 33.1°C (mean 31.1±0.11°C) and maximum 32.3–38.9°C (mean 35.3±0.16°C). While decreased protein level from 23% to 21 or 19% in starter diet (at fixed energy level of 2900 kcal ME/kg diet) did not alter gain in body weight but improved the feed efficiency, during finisher phase live weight gain was significantly depressed without altering feed efficiency with the result that higher (P<0.01) live weight gain was recorded at high CP in diet (23% and 21% in starting and finishing). The carcass traits, relative weight of visceral and immune organs, blood biochemical (except for SGOT and uric acid levels) and breast yield did not differ due to protein levels. The heterophil (neutrophil) to lymhphocyte ratio, alkaline phosphatases activities, and cellular as well as humoral immune-responsiveness were also similar in the three groups. The SGOT (P<0.01) and uric acid (P<0.05) levels were and feed cost of production increased significantly in amino acid supplemented low protein diets. The results indicated that best performance of broiler chickens was obtained at high levels of dietary protein (23 and 21% in starting and finishing diets) during extreme summer without affecting welfare parameters.