Abstract:
The amount and type of nutrient consumed by birds and the environmental temperature plus the interaction between them together with the strain and age differences had great effects on the overall performance of broilers in tropical countries. Three hundred and sixty, one day old unsexed broiler chicks were used to study the effects of strain differences on carcass characteristic of broilers fed two different levels of dietary protein. One hundred and twenty chicks from each of Ross, Cobb and Hubbard strain were divided into two groups the first, group (A ( was fed on diet contained (23%) crude protein as starter diet and replaced by a diet contained (21%) crude protein as finisher diet. The second group) B ( was fed a diet contained (21%) crude protein as starter diet then shifted to a diet containing (19%) crude protein. The environmental temperature during the study was 32-40c°. Final weights in Ross and Cobb (1249.33, 1196.23) were significantly (p<0.05) different from Hubbard strain (1111.23g). Hot carcass weight showed significant (p<0.05) differences among the three strains, they scored 1072.54, 1019.48 and 948.10 g in Ross, Cobb and Hubbard respectively. Results for carcass cuts showed that Ross and Cobb were significantly (p<0.05) different from Hubbard which recorded the lowest values. For internal organs weights strains were significantly (p<0.05) different, Hubbard strain yield the lowest values whereas the other two strains oscillate either coincide with Hubbard or with the third strain. High protein level (23%) significantly increased all carcass traits compared to low protein level (21%). Average live weight and hot carcass weight were 1252.08 and 1071.00g in high protein versus 1119.11 and 955.75 g in low protein level for the traits respectively. Two way interactions strain × protein level and strain ×age, significantly (p<0.05) affected internal organs, carcass yield and cuts. The experiment revealed that carcass yield at age 8 weeks was significantly higher in Ross strain than that in Cobb and Hubbard strains. Three way interaction, strain ×protein level × age significantly (p<0.05) affected body weight, carcass yield and cuts. . It is recommended to overcome decrease feed intake resulting from high ambient temperatures and to increase the level of protein in the diet to overcome decreased feed intake and to enhance broiler growth.
