Effect Of Dietary Protein Level And Supplementation Of Urea On Performance Of Broiler

To investigate the effect of dietary protein level and supplementation of urea on the performance, carcass quality, blood biochemical index, protein metabolism and body protein retention of broiler, 288 Avin commercial broilers aged 21d were divided into 6 groups, 4 replicates each group. The 3 basal diets (CP16, CP18 and CP20) were designed with 16%, 8% and 20% crude protein (CP) level and constant energy and main essential amino acids. The other 3 diets (CP16+U. CP18+U and CP20+U) were formed by supplementation of 0.1% urea in diets of CP16, CP18 and CP20. The 6 diets were assigned to 6 groups randomly. The experiment lasted 28 days. The results stated:1. The protein level of diets and supplementation of urea affect the feed intake (FI), weight gain (WG) and feed/gain (F/G) significantly. With diet CP level increasing, FI decreased, FI of CP16 and CP16+U were higher than that of other groups significantly (P<0.05). WG of CP16+U and CP18 were higher than that of other groups significantly (PO.05). F/G of CP16 and CP18+U were higher than that of other groups significantly (PO.05).2. With the CP levels of diets increasing, the abdominal fat decreased. The abdominal fat rate of CP20 and CP20+U were lower than other groups (P<0.05), depressed 33.77% and 42.54% than that of CP18 respectively. The breast meat rate of CP18 was higher than that of CP16 and CP16+U and CP20+U (P<0.05), increased 13.52%, 15.01% and 20.68% respectively. Supplementation of urea in diets has the trend of lowering the abdominal fat rate (P>0.05). Diet with 20% CP plus 0.1% urea lowered the breast meat rate significantly(P<0.05).3. CP level of diets and supplementation of urea affect BUN and BTP of broilers significantly. The difference of BUN level between CP16+U and CP20 is not significantly (P<0.05), but significant extremely between other groups (P<.01). Supplementation of 0.1% urea in diets can increase BUN level extremely (P<0.01). The BTP level of CP16+U and CP18 were higher than that of other groups extremely (P<0.01). Diet with 18% CP plus 0.1% urea lowered BTP level extremely (P<0.01).4. With the CP level of diets increasing, the apparent metabolic rate (AMR) of diet CP and amino acid were decreased (P<0.05). Supplementation of urea in diets has no effects on AMR of diet CP (P<0.05), but diet with 18% CP plus 0.1% urea lowered the AMR of non-essential amino acid and total amino acid significantly (P<0.05).5. Diet with 16% CP decreased the water content of excreta of broiler (P<.05).6. Body protein retention rate of broiler decreased with the CP level of diets increasing, but not significantly (P>0.05) .Supplementation of urea in diets has no effects on body protein retention rate of broiler (P>0.05) .The conclusion is:1. Though the requirement of all essential amino acids were meet to broiler, the moderate content of non-essential amino acid were needed in diet.2. Under the energy level and amino acid profile of this experiment, the appropriate CP level of diet is 18% for broilers aged 21 ~49d.3. The diet with 16% CP will hinder the performance of broilers because of the deficiency of non-essential amino acid, but diet with 16% CP plus 0.1% urea could compensate this deficiency and make broiler achieve higher performance. Urea can be used as a regulator of protein metabolism of broilers.