Effect of varying dietary energy and protein on broiler performance in hot climate

Abstract

The experiment was conducted to evaluate the effect of varying dietary metabolizable energy (ME) and crude protein (CP) concentrations on broiler performance during hot summer conditions. One day old straight-run (0.50 male and 0.50 female) Starbro broiler chicks ( n = 600) were randomly divided into 30 experimental units of 20 chicks each. Two levels of dietary ME (12.13 and 12.55 MJ/kg) and three levels of dietary CP (190, 210 and 230 g/kg) were used in a 2 × 3 factorial arrangement giving six dietary treatments. Level of essential amino acids were maintained in all the diets by supplementing low CP diets with crystalline amino acids. Each of the experimental diets was offered to five replicates from hatching to 28 d of age. At the end of the experiment, two birds from each replicate were randomly selected for data on dressing yield, breast meat yield, abdominal fat, and liver and gizzard weights. Increasing dietary ME significantly increased the BW gain, abdominal fat and liver weights, and protein and fat contents of the carcass whereas the dry matter of carcass was reduced by increasing dietary ME. Dietary CP had quadratic effects on BW gain, F:G, carcass weight, and dry matter and protein contents of the meat. Breast weight and fat contents of meat increased linearly with increasing CP of the diets. The low CP diets ( i.e., 190 g/kg) at high ME ( i.e., 12.55 MJ/kg) increased the BW gain, feed intake, carcass weight and improved F:G. However, lowest F:G was observed in birds fed 210 g CP and 12.13 MJ ME/kg of diet. Protein and fat contents of the carcass were increased in birds fed on diets having high CP and ME whereas dry matter contents of meat improved with high CP and low ME diets. The results of the trial showed a correlation between dietary CP and ME and hence the optimal value for one cannot be predicted without considering the other. Briefly, low CP with high ME diets improved the overall performance when environmental temperature ranged from 32 to 39 °C.