Effect of low crude protein diets with constant metabolizable energy on performance of broiler chickens from one to thirty-five days of age

A trial was conducted to study the effect of lowering dietary crude protein (CP) on the performance of broilers from 1 to 35 d of age. Four experimental broiler diets were formulated. Diet A served as control with 23, 22 and 20% CP in starter, grower and finisher periods, respectively while in diets B, C and D, the CP was reduced to 22, 21 and 20% in starter; 21, 20 and 19% in grower and 19, 18 and 17% in finisher period, respectively. All diets were isocaloric within a phase (2,925, 3,075 and 3,125 kcal/kg ME for starter, grower and finisher periods, respectively). Weight gain, feed intake, feed conversion ratio (FCR), total ME intake and energy efficiency ratio were similar across treatments. However, total protein intake decreased and protein efficiency ratio increased with low CP diets during all growth periods. The carcass characteristics were similar among treatments. In conclusion, the dietary CP level could be reduced without harmful effects on the performance of broilers when supplemented with limiting AA.