other ingredients in the diets were all the same among treatments. The experimental treatment design is shown in Table 2. All the diets were formulated according to an actual commercial formula for broilers [17] and to achieve approximately isocaloric and isonitrogenous diets. The analyzed nutrient composition of protein ingredients as well as the formulation and nutrient composition of the diets are shown in Tables 1 and 3. The DM, CP, and ash contents of the diets were determined according to AOAC methods [18], and the amino acid contents were analyzed by a Hitachi L-8800 automatic amino acid analyzer [19].
All birds were placed in stainless-steel wire cages 3-level battery and housed in an environmentally controlled room maintained between 34 and 31°C during the first week and then gradually decreased to 26°C at 21 d, after which it was maintained between 20 and 25°C until the end of experiment. The lighting program was 23 h of light for the first 2 wk and then 16 h of light to the end of the experiment. Birds were allowed ad libitum access to feed and water. The BW and feed intake of the birds were recorded by pen.