| In allusion to the reducing of poultry performance by low-protein diets,this study explored the suitable proportion of Arginine and Non-essential amino acids in low-protein diet of laying hens by comparing the application of synthetic amino acids and coated amino acids,and further clarified the limiting factors of the addition of synthetic amino acids in poultry low-protein diets,which were expected to provide new ideas and new methods for the efficient use of synthetic amino acids.Experiment 1,the aim of this study was to to explore the application of synthetic amino acids in low-protein diets in laying hens.The trial was divided into three parts,production performance trial,digestion and metabolism trial and amino acid metabolism trial.Digestion and metabolism trial and amino acid metabolism trial were processing in the fifth week of production performance trial.Digestion and metabolism trial was used to study the effect of Essential amino acids supplementation in low-protein diets on the digestibility of amino acids in laying hens by the means of indicator method,while amino acid metabolism trial was used to study the effect of Essential amino acids supplementation in low-protein diets on the releasing rate of amino acids in laying hens by the means of quantitative force-feeding method.Production performance trial was divided into two groups,the crude protein level is 16%in control group and 10%in low-protein group which supplied synthetic essential amino acids(Lys,Met,Thr,Trp,Ile,Leu,Arg,Phe,Val and His)up to control group level.The group and diet of digestion and metabolism trial with addition of 0.5%chromium sesquioxide were similar to production performance trial.The grouping of amino acid metabolism trial were similar to production performance trial and blood collection were processing in the first 2,4,and 6 hours from wing vein of each chicken that fored feed 30g diet.The results show that the egg laying rate,egg production,egg weight,body weight and feather quality of the low protein diet group were significantly lower than those of the control group(P<0.05),the feed-egg ratio was significantly higher than that of the control group(P<0.05);the color of egg yolk became deepen,hastelloy units increased and egg shape index became smaller;the digestibility of Glycine and Aspartic acid in the low protein group was significantly higher than that in the control group(P<0.05),and the digestibility of other amino acids was not significant(P>0.05);the total amino acids in the plasma of the low-protein group increased first and then decreased with the time passing,and the total amino acid in the control group showed a relatively stable state all the time.Compared with the control group,the plasma levels of urea in the low-protein group were significantly lower(P<0.05)and there was an interaction between time and treatment.With the time passing,uric acids of the plasma in the control group and low-protein groups gradually reduce.The results suggested that the production performance of laying hens fed with low-protein diet adding synthetic essential amino acids can not reach normal dietary levels.Experiment 2,the aim of this study was to explore the application of coated amino acids in low-protein diets in laying hens.This trail was divided into three parts,production performance trial,digestion and metabolism trial and amino acid metabolism trial.Digestion and metabolism trial and amino acid metabolism trial were processing in the ninth week of production performance trial.Digestion and metabolism trial was designed to study the effect of coated amino acids supplementation in low-protein diets on the digestibility of amino acids in laying hens by the means of indicator method,and amino acid metabolism trial was designed to study the effect of coated amino acids supplementation in low-protein diets on the release rate of amino acids in laying hens by the means of quantitative force-feeding method.Production performance trial was divided into three groups,control group(Con group,CP 16),synthetic essential amino acids supplementation of low-protein group(AA group,CP 14)and synthetic coated amino acids supplementation of low-protein group(MAA group,CP 12).The group and diet of digestion and metabolism trial with addition of 0.5%chromium sesquioxide were similar to production performance trial.The group and diet of amino acid metabolism trial were similar to production performance trial and blood collection were processing in the first 2,4,and 6 hours from wing vein of each chicken forced 30g feed.The results showed that the egg production rate and egg production of Con group were significantly higher than those of MAA group and AA group(P<0.05),the egg production rate and egg production of MAA group were significantly higher than those of AA group(P<0.05);the feed conversion rate of Con group was significantly lower than that of MAA group and AA group(P<0.05),the feed conversion rate of MAA group was significantly lower than that of AA group(P<0.05).The results of blood biochemical indexes in the fourth week showed that the total protein and urea content in the plasma of Con group were significantly higher than those of AA group and MAA group(P<0.05).The uric acid content in plasma of MAA group was significantly higher than that of AA group and Con group.The digestibility of Threonine of MAA group and AA group was significantly higher than that of Con group(P<0.05);the digestibility of Phenylalanine of MAA group was significantly higher than that of Con group and AA group(P<0.05);the digestibility of Leucine of MAA group was significantly higher than that of Con group(P<0.05);the digestibility of Valine of MAA group was significantly higher than that of AA group(P<0.05);the digestibility of Glycine of MAA group was significantly higher than that of Con group and AA group(P<0.05);the digestibility of Glycine of Con group was significantly higher than that of AA group(P<0.05).Compared with Con group and AA group,the releasing of amino acids of the MAA group was more stable in time.The results suggested that supplementation of coated amino acids in low-protein diets in laying hens can improve the performance reduced by low-protein diet,of which the reason is that the releasing rate of the coated amino acid group is more stable and more beneficial to the utilization of amino acids in laying hens.Experiment 3 studied the appropriate proportion of Arginine and Non-essential amino acids in laying hens with low protein diet.The trials were divided into 11 groups,including the control group,low protein groups(CP = 14%and 12%)in which both have five Arginine levels.The results showed that protein level of 14%with Arginine content of 0.85%(977mg/d)got the best egg production rate,egg production,feed to egg ratio and average egg weight.Also,the dietary protein level of 12%with the Arginine content of 0.67%(770mg/d)had the best egg production rate,egg production and feed to egg ratio.The results showed that supplement of essential amino acids with the form of synthetic amino acids in the low-protein diet changed the composition of amino acid in blood of laying hens and broke the balance of amino acid absorption,resulting in the decreasing of performance,which can be effectively alleviated by packaging of the amino acids.In addition,to maintain the healthy production of laying hens,it can be suggested that ratio of Arginine and Non-essential amino acid is 14.6%to 15.7%. |
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