The Minimum Crude Protein Requirement of Broilers Aged 0~3 Weeks

The experiments were conducted to investigate the influence of dietary crude protein(CP) levels on performance, serum biochemical indicators, hematopoietic parameters, immune function and nitrogen availability in broilers, then to estimate the minimum CP requirement of the maize soybean type diets in broilers aged 0 ~3 weeks in feeding and nitrogen metabolism trials. A total of 320 1-day-old male broilers were randomly assigned to 5treatments, which consisted of 8 replicates with 8 birds in each. Five levels each of CP(21.52%、20.58%、19.43%、18.03%and 17.03%) were fed in a corn-soybean basal diet during the feeding experiment from 1 ~17 old days and nitrogen metabolism trial from 17~21 old days according to a factorial experimental design. Results showed as follows: there were no significant differences(P 0.13)in average daily gain(ADFI), mortality, glucose, albumin, globulin, uric acid and triglyceride content in serum, hematopoietic parameters, ND antibody titers and nitrogen availability. Respectively, There were significant differences in average daily feed intake(ADG)(P0.07), feed conversion ratio(F: G)(P0.03), the total cholesterol(TC)(P0.10), total protein(TP)(P0.09)in serum, nitrogen retention(P0.0001)and nitrogen emissions(P0.0001). It not only increased the serum TP content and reduced nitrogen emissions more differently, but also made no negative effects on other indices when fed 19.43% CP diets compared with 21.52% level. However, it reduced ADG, TC in serum, nitrogen retention and emissions(P0.10) and increased F: G, TP in serum differently(P0.10)in 18.03 and 17.03%CP diets. Therefore, the minimum CP requirement of broilers aged 1 to 3weeks was suggested to be 19.43%.