Effects Of Different Dietary Protein Levels On Growth, Nitrogen Metabolism And CAT1mRNA Expression In Ileum Of AA~+Broilers

In the expressions,1350one-day fast large AA+broilers with the sameincubation, healthy were randomly divided into three groups(Ⅰ, Ⅱ and Ⅲ group).There were three replicates in each group. Ⅰ, Ⅱ and Ⅲ group were fed high,medium and low levels of protein dietary respectively. By feeding trail, metabolic testand slaughter test, the study was carried out to determine the effects of differentdietary protein levels on growth, serum and feces biochemical parameters. Meanwhile,the expression level of cationic amino acid transporter（CAT1）mRNA in ileum wasdetected by real-time quantitative PCR. To investigate the mechanism of CAT1regulate nitrogen metabolism in AA+broiler basic by the molecular level. This testhas important environmental significance in improving dietary protein utilization,reducing nitrogen excretion, reducing the NH3concentration, improving theenvironment and mitigating environmental pollution of NH3. Meanwhile, this studyhas important practical implications for improving growth performance, reducing feedresources waste, reducing production costs and mitigating environmental nitrogenpollution. Results are as bellow:1The level of dietary protein had a significant effect on body weight, ADG andF/G of AA+broiler. Compared with the high-protein group, the weight of15d ofmedium-protein group increased by3.89%(P>0.05), the weight of49d decreased by2.08%(P>0.05); Compared with the high-protein group, the weight of15d oflow-protein group increased by6.18%(P<0.05), the weight of49d decreased by4.79%(P<0.05), ADG increased by10.50%(P<0.01) during the8~15d, ADGdecreased by8.36%(P<0.05) during the16~30d; ADG of high-protein group was thehighest during the31~49d, and respectively increased by6.11%(P>0.05) and6.41%(P>0.05) compared with the medium-protein group and low-protein group; F/G ofmedium-protein group was the lowest during the16~30d, and respectively decreasedby3.68%(P>0.05) and28.80%(P<0.01) compared with the high-protein group and low-protein group.2Low-protein and high-protein diets respectively improved the protein synthesismetabolic capacity in early days and later period of AA+broiler, and low-proteingroup could reduce serum urea nitrogen level of the15d of AA+broiler. Comparedwith the high-protein group, serum STP level of15d of the medium-protein groupincreased by24.88%(P<0.05), serum SUN level of15d decreased by3.78%(P>0.05),and serum STP level of49d decreased by1.98%(P>0.05); Compared with thehigh-protein group, serum STP level of15d of low-protein group increased by32.95%(P<0.01), serum SUN level of15d decreased by15.14%(P<0.01), and serumSTP level of49d decreased by14.70%(P<0.05); Compared with the medium-proteingroup, serum SUN level of15d of low-protein group decreased by11.80%(P<0.05).3Fece TN level significantly improved in the medium-protein group andlow-protein group of AA+broiler; Fece UN level of low-protein group wassignificantly lower than the high-protein group. Compared with the high-proteingroup, Fece TN level of the medium-protein group decreased by10.77%(P<0.01),fece UN level decreased by11.11%(P>0.05); Compared with the high-protein group,fece TN level of low-protein group decreased by11.80%(P<0.01), fece UN level ofdecreased by33.56%(P<0.01).4Dietary protein level had extremely significant effect on NH3concentrations.Low-protein group could significantly reduce NH3concentration in the henhouse.Average NH3concentration of12d,20d and34d of high-protein group were higherthan medium-protein group7.46%,7.42%and2.70%respectively(P<0.01); AverageNH3concentration of12d,20d and34d of medium-protein group were higher than thelow-protein group1.11%(P>0.05),1.89%(P<0.01) and3.66%(P<0.01).5With the reducing of protein levels, CAT1mRNA expression level appeared onthe rise, but had no significant difference (P>0.05).Conclusion: The level of dietary protein had a significant effect on the growthperformance of AA+broiler. To feed broiler low, medium and high-protein levels (CP:18.5%,19%and19.5%) could achieve the best growth performance; The low-proteingroup was extremely significant to increase serum STP level of15d of AA+broiler,the high-protein group significantly increase serum STP level of49d of AA+broiler; Dietary protein levels had no significant effect on serum SUA level of AA+broiler,but the low-protein group was extremely significant in decreasing serum SUN level of15d of AA+broiler. Medium-protein group and low-protein group were extremelysignificant to reduce fece TN content of AA+broiler; Dietary protein levels had nosignificant effect on fece UA content; Fece UN content of the low-protein group wassignificantly lower than the high-protein group; In different growth stages of AA+broiler, different protein levels were extremely significant to effect on NH3concentration in hire. With the reducing of protein levels, CAT1mRNA expressionlevel appeared on the rise, but had no significant difference.