The Studies Of Optimal Dietary Metabolizable Energy And Crude Protein Levels For Dawufen No.1 Commercial Layer Chicks From 0 To 9 Weeks Of Age

To determine the optimum dietary metabolizable energy(ME)and crude protein(CP)levels of Dawufen No.1 commercial layer chicks during 0~4 weeks and 5~9weeks,the effects of dietary ME and CP levels on the growth performance,body size traits,organ indexes and serum biochemical of pullets from hatching to 9-week-age were evaluated,and the regression models between the dietary ME or CP levels and the testing indexed in trial were build.Experiment 1: 3×3 two factors experiment was adopted.Nine experimental dietary were prepared,the ME levels in the diets were12.01 MJ/kg,12.51 MJ/kg,13.01 MJ/kg,respectively,and the CP levels in the diet were 19.81%、20.81%、21.81%.810 1-day-old good health Dawufen No.1 commercial layer chicks with the same genetic background,similar body weight and skeleton development were randomly divided into 9 group with six replicates per group and 15 chichs per replicates.The experiment last for 28 days.The results showed that:(1)Dietary ME levels had significant effect on average daily weight gain(ADG),average daily feed intake(ADFI),feed gain ratio(F/G)of and final keel length,final body weight,final duodenum and ileum relative length(P <0.05),and there was significant quadratic curve relationship between dietary ME level and ADFI,F/G,the contents of serum glucose(GLU),triglyceride(TG)or total cholesterol(TC)(P<0.05).(2)Dietary CP level had significant effects on the chest width,liver index,duodenum relative length and ileum relative length of the layer chick at the age of 4 weeks(P<0.05),and there was a significant quadratic curve relationship between dietary CP level and chest breadth(P<0.05).(3)The interaction of dietary ME and CP levels had significant effects on ADG,F/G,duodenum relative length,ileum relative length and serum TG content(P<0.05).(4)According to fit quadratic curve,the best levels of ADFI,F/G,serum GLU,TG and TC contents were obtained when dietary ME levels were 6.991,12.979,10.524,11.968 and 11.775 MJ/kg,respectively,and the best levels of liver index and chest breadth were obtained when dietary CP levels were 20.402% and 20.730%,respectively.Experiment 2: 3 ×3 two factors experiment was adopted.Nine experimental dietary were prepared,the ME levels in the diets were 12.42MJ/kg,11.92 MJ/kg,11.42 MJ/kg,respectively,and the CP levels in the diet were 18.75%、17.75%、16.75%.810 28-day-old good health Dawufen No.1 commercial layer chicks with the same genetic background,similar body weight and skeleton development were randomly divided into 9 group with six replicates per group and 15 chichs per replicates.The experiment last for 35 days.The results showed that:(1)Dietary ME levels had significant effect on the tibia length,chest breadth,keel length,serum triglyceride content of layer chicks aged 9 weeks(P <0.05),and there was significant quadratic curve relationship between dietary ME level and chest breadth,keel length,serum triglyceride content(P<0.05).(2)Dietary CP level had significant effects on the body weight and chest breadth of layer chicks aged 9 weeks and the ADG of layer chicks aged 5 to 9 weeks(P<0.05)and there was a significant quadratic curve relationship between dietary CP level and final body weight(P<0.05).(3)The interaction of dietary ME and CP levels had significant effects on chest breadth,keel length and serum triglyceride content(P<0.05).(4)According to fit quadratic curve,the best levels of chest breadth,keel length,serum triglyceride content were obtained when dietary ME levels were 11.420,11.483 and 11.379 MJ/kg,respectively,and the best levels of body weight were obtained when dietary CP levels were 17.902%.