Effect of Dietary Energy and Protein on Growth Performance and Carcass Traits of Mamourah Cockerels
Kh. El. Sherif,
A.M. Abd El-Khalek
Background: Dietary energy and protein are the most important determinants of least-cost feed formulation. So, the concurrent increase in feed prices and demand on animal proteins for humans necessitate an urgent need to define the optimal dietary protein and energy levels for growing poultry. Materials and Methods: A study with a factorial arrangement of treatments (2×3) was done to investigate the effects of two dietary protein levels (18 and 20% CP), each with three metabolizable energy levels (3100, 3000 and 2900 kcal ME kg1) on growth performance, nutrient digestibility, carcass traits and blood parameters of Mamourah cockerels. One hundred eighty birds were randomly allocated to 6 experimental groups, each with three replications and kept in floor pens in an open-sided house. Thus, six diets were formulated and fed to the experimental birds and managed similarly from 6-14 weeks of age. Results: Feeding the 20% CP diets throughout the experiment positively affected feed intake and weight gain of cockerels and negatively affected protein efficiency ratio and economic efficiency compared with the 18% CP diets but feed conversion ratio and efficiency of energy utilization were not affected. Conversely, birds fed the 18% protein diets exhibited significantly higher digestibility of dry matter, organic matter, crude protein and ether extract than those fed the 20% protein diets but digestibility of other nutrients were not altered. Dietary protein level had no effect on almost all carcass traits and blood parameters examined. However, decreasing dietary ME level did not affect feed intake or nutrient digestibility but positively affected growth performance. Carcass traits were not affected by decreasing dietary ME level but when it reached 2900 kcal kg1 percent abdominal fat was significantly reduced and the percentages of carcass yield, total edible parts and liver were negatively affected. Dietary energy level had no effect on plasma constituents of birds but cholesterol concentration decreased when ME level reduced to 3000 or 2900 kcal kg1. The interactions between dietary protein and energy levels were not significant for most variables examined. Conclusion: Taking the economic aspect into account, optimal dietary CP and ME levels for growing Mamourah cockerels are suggested to be 20% CP and 3000 kcal kg1.
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