Effects Of Different Dietary Protein Levels On The Growth Performance,Non-specific Immunity And Antioxidant Capacity Of Rhynchocypris Lagowskii Dybowski

The juvenile Rhynchocypris lagowskii Dybowski with initial body weight(6.98±0.01 g)were studied.Fish meal,soybean meal,rapeseed meal and cottonseed meal were the main protein source;corn oil and fish oil were the main fat source.In order to evaluate the effect of different dietary protein level on the growth performance,non-specific immunity and protein metabolism enzymes,five diets with different protein levels(24.98%,30.02%,34.99%,40.01% and 44.98%),the same energy and the same fat level(6.0%)were fed Rhynchocypris lagowskii Dybowski for 8-weeks.These results showed that: 1.Effects of protein levels on growth,feed utilization and muscle nutrient composition of Rhynchocypris lagowskii DybowskiUnder the current conditions,with the increase of dietary protein level,the final body weight,weight gain rate and specific growth rate of Rhynchocypris lagowskii Dybowski were decreased after increased.The body weight,weight gain rate and specific growth rate of 34.99% and 40.01% groups were significantly higher than those of 24.98% group(P<0.05).Similarly,with the increase of dietary protein level,the feed efficiency ratio and protein efficiency ratio of Rhynchocypris lagowskii Dybowski showed the same trend,and the feed efficiency ratio and protein efficiency ratio of 40.01% group were significantly higher than those of 24.98% group(P<0.05),but there were not significant difference in 30.02%,34.99% and 44.98% groups(P>0.05).By broken-line model analysis,the highest specific growth rate was found in the 35.89% protein levels.And when the 36.11% protein levels showed the highest feed efficiency ratio.With the increase of dietary protein level,the crude protein content in muscle of Rhynchocypris lagowskii Dybowski was decreased after increased the crude protein of 40.01% group was significantly higher than that of 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).However,with the increase of dietary protein level,the crude fat in muscle of Rhynchocypris lagowskii Dybowski showed the reverse trend.The crude protein of 40.01% group was significantly lower than that of 24.98%,30.02% and 34.99% groups(P<0.05),but there were not significant difference with 44.98% groups(P>0.05).2.Effects of different protein levels on non-specific immune-related enzyme activities of Rhynchocypris lagowskii DybowskiUnder the current conditions,with the increase of dietary protein level,the ACP,AKP,LZM and SOD activities of Rhynchocypris lagowskii Dybowski were decreased after increased.The ACP,AKP,LZM and SOD activities of 40.01% group were significantly higher than those of 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).3.Effects of different protein levels on protein synthesis and metabolic enzyme activity of Rhynchocypris lagowskii DybowskiUnder the current conditions,with the increase of dietary protein level,the RNA content and RNA/DNA of Rhynchocypris lagowskii Dybowski were decreased after increased.The RNA content and RNA/DNA of 40.01% group were significantly higher than those in 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).By analysis of quadratic polynomial regression,when the protein levels was 36.01%,the RNA content was the highest.When the protein levels was 35.91%,the RNA/DNA was the highest.Under the current conditions,with the increase of dietary protein level,the AST activities of Rhynchocypris lagowskii Dybowski was increased.The AST activities of 40.01% and 44.98% groups were significantly higher than that in 24.98%,30.02% and 34.99% groups(P<0.05).But the activity of AST of 30.02% and 34.99% groups showed no significant difference(P>0.05).The same result was found in 40.01% and 44.98% groups(P>0.05).With the increase of dietary protein level,the ALT activities of Rhynchocypris lagowskii Dybowski were significant increased(P<0.05).With the increase of dietary protein level,the hepatopancrea protease of Rhynchocypris lagowskii Dybowski was decreased after increased,but there was no significant differences among them(P>0.05).With the increase of dietary protein level,the protease activities in fore intestine and middle intestine of Rhynchocypris lagowskii Dybowski were decreased after increased,when the protein level were 40.01%,the protease activities in fore intestine protease and middle intestine were significantly higher than that in 24.98%,30.02% and 44.98% group(P<0.05),but there were no significant difference with 34.99% group(P>0.05).With the increase of dietary protein level,the protease activies in hind intestine of Rhynchocypris lagowskii Dybowski was decreased after increased,when the protein level were 40.01%,the protease activity was significantly higher than that in 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).4.Effects of different protein levels on antioxidant capacity of Rhynchocypris lagowskii DybowskiWith the increase of dietary protein level,the MDA content of Rhynchocypris lagowskii Dybowski were increased after decreased,when the protein level were 40.01%,the MDA content was significantly lower than those in 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).With the increase of dietary protein level,the CAT,T-AOC,GSH-Px,GSH and GSSG of Rhynchocypris lagowskii Dybowski were decreased after increased,when the protein level were 40.01%,the MDA content was significantly higher than those in 24.98%,30.02%,34.99% and 44.98% groups(P<0.05).Therefore,based on the above factors,with the increase of dietary protein level,the Growth performance index,non-specific immunity,protease activity and antioxidant index of Rhynchocypris lagowskii Dybowski were decreased after increased.