Effects of high dietary energy, with high and normal protein levels, on broiler performance and production characteristics

This study was conducted to investigate the effect of high metabolizable energy diets with normal or wide metabolizable energy to crude protein ratios (ME:CP) on the performance, carcass characteristics, body composition and blood parameters of broilers fed from 1 to 56 days of age. The chicks were allotted into 7 groups; one control and 6 tested. The birds were fed starter, grower and finisher diets. The control diet was formulated according to the NRC of poultry (1994) and the other six diets contained three different levels of high energy diets (3275, 3350 & 3425 kcal/kg; one level for each two groups). The first three tested groups were pointed for as the ''normal calorie-protein ratio” groups in which the CP increased in relation to the increased ME, keeping the normal NRC ratio. In the second three tested groups, named “wide calorie-protein ratio” groups, the dietary protein was kept at the NRC levels leading to ratios wider than that of the NRC. Results showed that chicks fed high ME diets with normal energy to protein ratio grew faster, and used feed more efficiently than chicks fed the control diets. However, feeding diets with high ME and normal protein NRC-levels slightly improved the weight and feed conversion. The visible fat and fat retained in the body was higher in all tested groups compared to the control. However, the blood parameters had no significant variations among the treatments, except for ALT which had an increased response to increased dietary energy density. In conclusion, increasing the dietary ME level without increasing the crude protein level provided moderately economic returns and lesser improvement in the performance of broilers. However, increasing of dietary ME with normal ME:CP ratio resulted in increased broiler performance and higher economic return.