| As the deficiency of dietary protein,due to the serious environmental problems caused by large amounts of nitrogen in livestock and poultry waste,nutritionists began to focus on the allocation of low protein diets.According to the physiological needs of animal,reduce the level of protein and add amino acid to adjust the essential amino acid and non-essential amino acid in the best condition in quantity and proportion,so that animals can achieve the maximum protein bioavailability and reduce the requirement of crude protein feed produced by animal production in this mode.Two hundreds one-day-old Arbor Acres(AA)broilers were randomly assigned to four groups with five replicates of 10 chicks.The basal diet was formulated based on National Research Council(NRC,1994).The experimental diets were formulated based on NRC(1994)and reduced 3% crude protein by the standard.Broiler chicks were reared from 1 to 21 days of age in the three layers of cage,and 22 to 42 days of age on the ground.The broilers were randomly subjected to one of the following 4 treatments for 42 days: the control group broilers feed basal diets without essential amino acids supplementation,the experimental diets were B,C and D,in 1 to 21 days of age broilers fed diets with 0.1% DLM(DL-Methionine),0.22% Lys(L-lysine)and 0.1% DLM+0.22% Lys supplementation with 3% crude protein reduced by basal diets respectively,in 22 to 42 days of age broilers fed diets with 0.1% DLM(DL-Methionine),0.26% Lys(Llysine)and 0.1% DLM+0.26% Lys supplementation with 3% crude protein reduced by basal diets respectively.The results are as follow: The balance of amino acids in low protein diets significantly increased the feed intake in Group C and D at the finisher period and the whole period,and decreased the FCR(feed conversion rate)at starter period(P<0.05).At 21 days of age,Group D had the highest breast weight compared with other groups(P<0.05).Group B had the highest abdominal fat weight and abdominal fat ratio(P<0.05).At 42 days of age,Group D had the highest thigh weight,thigh ratio and liver weight(P<0.05).Group D had the highest breast weight but there was no statistical significant among different groups in the present study(P>0.05).The serum profile results showed as: at 21 days of age,Group C extremely significant increased the concentration of uric acid(UA)in serum of broilers(P<0.01).Group D significantly increased the concentrations of total protein(TP)and globulin(GLOB)in serum of broilers(P<0.05).Group B and D in low protein diets did not affect the concentrations of blood urea nitrogen(BUN),UA,TP,albumin(ALB)and GLOB in serum of broilers at 42 days old,but there was a trend of decrease concentration of BUN compared with the control(P>0.05).Antioxidant properties:at 21 days of age,Group D significantly enhanced the activities of GSH-Px in liver and SOD in serum(P<0.01,P=0.05),reduced the content of MDA in serum and liver(P<0.05);Group B and D significantly enhanced the activity of T-AOC in serum and liver(P<0.01),decreased the ability of inhibiting ·OH(P<0.05).At 42 days of age,Group B and D significantly enhanced the activities of GSH-Px in serum and SOD in serum and liver(P<0.05,P<0.01);low protein diets supplemented amino acids reduced the content of MDA in serum and liver(P<0.01).Nitrogen balance :low protein diets significantly reduced excretion and nitrogen intake of broilers(P<0.05),Group D significantly reduced the nitrogen excretion of broilers(P<0.05).Significantly reduced nitrogen intake in broilers(P<0.05).Group C and D significantly reduced the excretion,nitrogen excretion and nitrogen excretion rate of broilers(P<0.05).The ammonia excretion in chicken manure was significantly reduced(P<0.05).Histological morphology of intestinal tract: group B and D Significantly increased villus length and crypt width of jejunoileum(P<0.01).The villus width,epithelial cell thickness,villus length and crypt depth ratio were significantly increased(P<0.01).Low protein diets significantly increased villous width and recess width of duodenum(P<0.01).At day of 42,The width of intestinal villus significantly increased,and crypt depth decreased significantly(P<0.01).The length of ileum in Group B and Group D were significantly increased(P<0.01).The ratio of intestinal villus height and crypt depth in Group D increased significantly(P=0.05).The width of ileum recess in Group B and D were significantly higher than that in control(P<0.05).The ratio of duodenal intestinal villus length to crypt depth was significantly higher than that in the control(P<0.01).the thickness of duodenum epithelial cells in Group C increased significantly(P<0.01).Amino acid transporter associated genes: Group D down-regulated the mRNA expression of SLC38A1 gene in jejunoileum(P<0.05).The expression of SLC7A1 gene in duodenum was down-regulate(P<0.05).At 42 days of age,Low protein diets upregulated the mRNA expression of SLC38A1 gene and SCL6A14 gene(P<0.05).Group B up-regulated the SCL6A14 gene and down-regulated the mRNA expression of SLC7A7 gene(P<0.05).Significantly up-regulated the mRNA expression of SLC7A1 gene in experimental group.Group B and C down-regulated mRNA expression of SLC7A9 gene in duodenumLow protein diets adjusted amino acid balance can improve the length of intestinal villi,decrease crypt depth and improve digestion and absorption ability of broiler intestine,metabolic status and amino acid balance of protein in broiler,change the expression of amino acid transporter related genes in mrna,these resulted that the body weight gain and feed utilization rate of broilers were improved,increased feed intake in late feeding and whole feeding,The low protein diet improved the antioxidant performance of broilers decreased the lipid peroxidation,also decreased the excretion of nitrogen,reduced the ammonia emissions in the feces,and reduced the environmental pollution. |
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