Study on appropriate levels of metabolizable energy and crude protein in diets for Yanjin black-bone chickens aged 1 to 6 weeks
LI Hongwei
ZHOU Anshu
WANG Xingxian
ZHANG Shiyun
YANG Liangyu
XIANG Bin
TAO Linli
NIU Guoyi
Abstract：The experiment aimed to investigate the effects of dietary metabolizable energy and crude protein levels on the growth performance,metabolic rates,and serum biochemical indices of Yanjin black-bone chickens.A total of 450 healthy one-day-old Yanjin black-bone chickens(half male and half female)with similar body weight were randomly divided into 15 groups according to a 3×5 two factor experimental design,with five replicates per group and six chickens per replicate.Factor 1 was metabolizable energy level(12.00,12.60,13.20 MJ/kg)and factor 2 was crude protein level(17.00%,18.00%,19.00%,20.00%,21.00%).The pre-test period lasted for three days,and the formal test period lasted for 42 days.The results showed that the final weight and average daily gain with a metabolizable energy of 12.60 MJ/kg were significantly higher than those at other metabolizable energy levels(P<0.05).The final weight and average daily gain with a crude protein content of 20.00%were the highest,and those with a crude protein content of 17.00%were significantly lower than those at other crude protein levels(P<0.05).When the dietary metabolizable energy was 12.60 MJ/kg with 21.00%crude protein and when the metabolizable energy was 13.20 MJ/kg with 18.00%crude protein,the feed to gain ratio reached the lowest.The gross energy and crude protein metabolic rates at metabolic energy levels of 12.00 MJ/kg and 12.60 MJ/kg were significantly higher than those at 13.20 MJ/kg(P<0.05).The metabolic rates of glycine,arginine,valine,isoleucine and phenylalanine at a metabolic energy level of 13.20 MJ/kg were significantly lower than those at other metabolic energy levels(P<0.05).The gross energy and the metabolic rate of crude protein with a content of 20.00%were the highest.The metabolic rates of threonine,valine,leucine and phenylalanine in the group with a crude protein content of 21.00%were significantly higher than those in all other groups except the one with a crude protein content of 20.00%(P<0.05).The valine metabolic rate was the highest when the dietary metabolizable energy was 12.60 MJ/kg with 21.00%crude protein.The content of uric acid(UA),with a metabolic energy of 13.20 MJ/kg,was significantly lower than that of the metabolic energy of 12.00 MJ/kg(P<0.05).The total cholesterol(TC)content at a metabolic energy of 12.00 MJ/kg was significantly lower than that at other metabolic energy levels(P<0.05).The triglyceride(TG)content with a crude protein level of 19.00%was significantly lower than that of other crude protein levels(P<0.05).When the metabolic energy was 12.00 MJ/kg and the crude protein was 19.00%,the glucose(GLU)content was the highest.The study shows that the optimal dietary metabolizable energy level is recommended to be 12.60 MJ/kg and the crude protein level is 20.00%for Yanjin black-bone chickens aged 1 to 6 weeks.
Keywords：Yanjin black-bone chickensmetabolizable energycrude proteingrowth performancemetabolic rateserum biochemical indices
Publication Date：2025-12-16
Online Publishing Date：2026-01-31(First online date of this platform, not the publication date of the document)
Pages：8( 43-50 )