Performance of Broilers Fed Low Dietary Protein Levels with or Without Supplementation of Lysine and Methionine

Broiler diets low in crude protein (CP) by 2 and 4% over the optimum levels of 23% an starter and 20% in finisher rations were tested in a feeding trial from 8 to 49 d of age. The two low CP diets were fed either as such or after supplementation with methionine and lysine equivalent to that of control. Two control diets were formulated to contain fish-soybean combination (FM control) or soybean meal alone (SBM control) as the main source of protein. All the six diets were ted ad libitum to 180 broiler chicks, distributed equally into six groups with three replicates each. Broilers fed FM control diet were heavier (2052 g) than those fed 19 or 21% CP, at 7wk of age. Supplementation of methionine and lysine to the diet containing 21% CP improved growth equivalent to that of the controls but not the diet with 19% CP. Feed intake was not influenced by the level of CP in diet hut, feed conversion efficiency was significantly better in FM control diet and also in groups offered 21% CP supplemented with amino acids. The protein efficiency ratio was better when CP was higher at 23% and addition of amino acids did not improve protein conversion efficiency. CP level did not influence the eviscerated yield or giblet weight. But, abdominal fat increased with decrease in CP content of diet and supplementation of amino acids marginally reduced fat content, particularly sat 21% level. However, feed cost kg live weight favoured low protein diets without supplementation of amino acids. Further, it was observed that diets containing FM or SBM alone as protein source had similar effect on the performance of broilers implying that SBM, adequately balanced for methionine and lysine can replace fish meal from broiler diets.