Dietary Crude Protein Requirement Of Broilers From22 To 42 Days Of Age

An experiment was conducted to investigate the effect of dietary crude protein(CP) 1evel on growth performance, carcass quality, serum biochemical parameters, immune indexes and nitrogen availability in broilers, so as to estimate the minimum CP requirement of broilers fed corn-soybean diet from 22 to 42 days of age. A total of 360 22-day-old male broilers were randomly assigned to 5 treatments with 10 replicates per treatment and 6 birds each replicate.The birds were fed the diet containing CP 19.87%(control), 18.84%, 17.63%, 16.81%, 15.75% or 14.88% for 21 days. The feces were collected from 38 to 42 days of age. The results showed as follows:dietary CP level affected average daily gain, ratio of feed intake to body gain, percentage of abdominal fat, drip loss, L* and a* values of breast meat, a* and b*values of thigh meat, content of total cholesterol, triglyceride, and uric acid in serum, ND antibody titer, nitrogen content in feces and availability of dietary nitrogen(P < 0.05) of broilers, respectively. Compared with the control, no differences were observed(P > 0.05) in the above mentioned indexes for broilers fed diets containing 17.63% of CP, however, nitrogen content in feces was significantly lower(P < 0.05). Broilers fed diets containing 16.81% or lower CP had lower(P < 0.05) daily gain and ND antibody titer, as well as higher(P < 0.05) ratio of feed intake to body gain, abdominal fat, drip loss of breast meat, serum total cholesterol and triglyceride content compared with the control, respectively. Therefore, the minimum dietary CP requirement of broilers from 22 to 42 days of age was suggested as 17.63%.