Effect of Low Levels of Dietary Crude Protein with Constant Metabolizable Energy on Nitrogen Excretion, Litter Composition and Blood Parameters of Broilers

A study was conducted to determine the effect of lowering dietary crude protein (CP) with optimum limiting amino acids (AA) levels on nitrogen (N) excretion, litter composition and blood parameters of broilers from 1 to 35 days of age. Four isocaloric broiler diets were formulated. Diet A served as control with 23, 22 and 20% CP, while in diets B, C and D, the CP was reduced to 22, 21 and 20%; 21, 20 and 19% and 19, 18 and 17% with 2925, 3075 and 3125 kcal/kg energy for starter, grower and finisher periods, respectively. A total of 1760, one day-old Hubbard broiler chicks were randomly divided into 16 experimental units, 110 chicks in each unit and each diet was offered to four experimental units at random. Results suggested that N excretion decreased (P<0.05), while N retention and its excretion as percent of N intake were not different among treatments. Low CP diets significantly reduced (P<0.05) the moisture and N content of the litter; although ash content was not altered. The plasma uric acid concentration decreased (P<0.05) and triglycerides concentration increased significantly by lowering the dietary CP content. However plasma glucose, triiodothyronine and thyroxine concentrations were unaffected. In conclusion, lowering dietary CP resulted in reduced N excretion without any adverse effect on N retention, which was also expressed in the levels of plasma metabolites and hormones. © 2010 Friends Science Publishers