Studies On The Optimal Protein, Methionine Requirements And Ideal Protein Pattern Of Laying Hens In Low Energy Level

This study was conducted to determine the influence of dietary methionine and crude protein levels on the laying performance, egg quality, as well as conventional nutrients digestibility in commercial Hy-line laying hens. The ideal protein pattern of Hy-line hens was established by model fitting.Experiment 1: A 3×3 factorial trial with three crude protein levels and three methionine levels was conducted with Hy-line laying hens ( n = 1200) for 8 weeks to determine the influence of dietary methionine and crude protein levels on the performance in commercial Hy-line laying hens. The diet was based on corn-soybean meal, The 1200 Hy-line hens were randomly divided into 10 treatment groups (5 replicates of 24 hens per treatment ) , ten diet treatments were formulated based on crude protein content of 15.3 % , 15.9 % and 16.5 % ,methionine content of 0.29 %, 0.34 % and 0.39 %, the control group was designed according to GB (2004).The results showed that: (1) there was no significant effect on the laying performance in the peak stage (p>0.05) when the Methionine levels varied from 0.29% to 0.39% and the protein levels varied from 15.3% to 16.5% in diet.(2) The analysis indicated that C2 group (energy was 2600 kcal/kg, crude protein was 16.5% and methionine was 0.34%) was the best among the 9 treatment groups.Experiment 2: This study was conducted to determine the true digestibility of dietary amino acid and availability of protein dietary in commercial Hy-line laying hens. All laying hens were allotted to ten treatments in a completely randomized design,every treatment has 5 replicates (4 hens per replicate).The two-factor anova showed that:(1) The dietary with different protein levels had significant effects on nitrogen ingestion and nitrogen retention (P <0.05); The dietary with different methionine levels had significant influences on nitrogen excretion, nitrogen retention and the efficiency of nitrogen retention(P <0.05), the protein and methionine interaction had significant effects on nitrogen ingestion and nitrogen excretion (P <0.05),the latter reached an extremely significant level (P <0.01).(2)The dietary with three kinds of protein levels had significant effects on the true digestibility of arginine and alanine (P <0.05); the dietary with three kinds of methionine levels had significant influences on the true digestibility of glycine, methionine and tyrosine (P<0.05), the protein and methionine interaction had no significant influence on the true digestibility of all the amino acids(P>0.05).Experiment 3: A 3×3 factorial trial with three crude protein levels and three methionine levels was conducted with Hy-line laying hens ( n = 1200) for 8 weeks to determine the influence of dietary methionine and crude protein levels on the egg quality in commercial Hy-line laying hens.The results showed that: there were no significant effects (P> 0.05) on the nutritional composition and quality of eggs when the diets contained methionine 0.29% -0.39% and protein 15.3% -16.5%.Experiment 4 : The experiment was conducted to determine the requirentments of amino acid in Hy-line laying hens. The ideal protein pattern of hy-line hens was obtained by analyzing the amino acid content of carcass, feathers and eggs. Assumed the lysine is 100, the optimum pattern of some main amino acids was as follows: Arg: Gly: The: Pro: Val: Met: Cys: Ile: Leu: Phe: His: Lys = 112: 88: 78: 92: 116: 43: 54: 92: 151: 94: 41: 100.