Effect of Dietary Protein Levels and Strain on Growth Performance and Carcass Characteristic of Heat Stressed Broiler Chicks

An experiment was carried out to study the effect of heat stress on growth performance and carcass characteristics of three broiler strains fed two different levels of dietary protein. Three hundred and sixty, one day old unsexed broiler iv chicks, were used 120 from Ross strain, 120 for Cobb strain and 120 for Hubbard strain. The experiment was executed complete randomize design factorial arrangement. The number of chicks of each strain was divided into two groups, with six replicates (10 chicks per each). Group A of each strain was fed on diet containing 23% crude protein and 3000 Kcal/kg Metabolizable energy, as starter diet for the first four weeks of age, and then replaced by a diet containing 21% crude protein and 3000 Kcal/kg Metabolizable energy as finisher diet. Group B for each strain was fed a diet containing 21% crude protein and 3000 Kcal/kg Metabolizable energy as starter diet for the first four weeks and then shifted by the diet containing 19% crude protein and 3000 Kcal/kg Metabolizable energy as finisher diet. Feed intake, body weight gain and feed conversion ratio were recorded on weekly basis throughout the entire duration of experiment. Feed intake per bird for Ross, Cobb and Hubbard strains were as follows: 3127.54, 3074.69 and 2850.17g, respectively. At the end of the experiment 24 birds from each strain were slaughtered (12 birds for each group) at the age of 7th week and 8th week. The results revealed that the birds in group A (fed on high protein diet) of each strain had significantly (P<0.05) higher live body weight and growth performance than group B (fed low protein diet). The Ross strain got the significantly (P<0.05) higher live body weight than Cobb and Hubbard strains. Two way interaction (strain*diet, strain*age) significantly increased live body weight and carcass yield, whereas the interaction between diet*age was not significantly. The experiment revealed that carcass yield at age 8 weeks was significantly increased in Ross strain that in Cobb and Hubbard strains. Three way interaction between variances significantly (p