Effects Of Rice Protein Hydrolysate On The Growth,Metabolism And Muscle Quality Of Ictalurus Punctatus

In order to solve the contradiction between the rising demand and insufficient production of fish meal,rice protein hydrolysate was used to replace fish meal to explore the effects on the growth,metabolism and quality of muscle of Ictalurus punctatus,and tried to increase the utilization rate of rice protein hydrolysate by supplementing lysine and fish paste hydrolysate.The feeding experiment was divided into three parts.The first part,fish meal in the control diet(10%)was replaced by rice protein hydrolysate(0,2.5%,5.0%,and 7.5%)to formulate four isonitrogenous and isolipidic diets(designed as FM,RP2.5,RP5.0,RP7.5).The second part,the 0.25% lysine was added into the diet of RP7.5 group to formulate on diet(designed as Lye7.5).The third part,the fish meal in the RP5.0 diet was replaced by fish paste hydrolysate(2.5%,and 5.0%)to formulate two diets(designed as FP2.5,FP5.0).7 groups of experimental feeds were prepared,and 7 groups of Ictalurus punctatus with similar specifications(6.50±0.01g)were fed respectively(3 replicates in each group,35 tails per replicate).The experiment result shows:Chapter 2: compared with the FM group,the weight gain rate(WGR)was higher in the RP2.5 group(P<0.05),and was not different from the RP5.0 group(P<0.05),although it was significantly lower in the RP7.5 group(P<0.05).The digestive enzyme activity of liver and intestines showed similar changes to WGR.The villi length and goblet cells in the intestine had better performance in RP2.5 group.The intestinal microbial composition of the RP2.5group was not significantly different from that of the FM group,but the abundance of some microorganisms involved in sugar metabolism increased(P<0.05).The number of microorganisms in the RP7.5 group increased significantly,but the abundance of conditional pathogenic bacteria such as Aeromonas and Vibrio also increased significantly.The area of muscle fibers increased significantly in RP7.5(P<0.05),but the density of muscle fibers decreased significantly in RP7.5(P<0.05).The expression of myod gene in the muscles of RP7.5 group was significantly down-regulated(P<0.05),and the expression of mstn was significantly up-regulated(P<0.05).The activities of catalase(CAT)of RP2.5 and RP5.0 were significantly higher than FM(P<0.05).Chapter 3: compared with the RP7.5 group,the WGR in the Lye7.5 group was significantly increased(P<0.05),and there was no significant difference between FM and Lye7.5 group(P<0.05).The activities of GPT and GOT in liver were significantly higher(P<0.05).The activities of Amylase,Trypsin,AKP and NKA in intestine were also significantly increased(P<0.05).At the same time,the length of intestinal villi increased significantly(P<0.05).The hardness and chewiness of the muscles were significantly increased(P<0.05),and the density of muscle fibers was significantly increased(P<0.05).The expression of myod and the activity of CAT and GSH-PX increased significantly(P<0.05).Chapter 4: compared with the RP5.0 group,the WGR of the FP2.5 and FP5.0 groups increased,but no significant difference.The activities of Amylase,Trypsin,AKP and NKA were significantly increased.The addition of fish paste hydrolysate has a significant effect on the muscle quality.The lutein content of skin decreased significantly,while the activity of tyrosinase increased significantly(P<0.05).The values of brightness and the color difference decreased significantly.The hardness,springiness,adhesiveness,chewiness and fiber density of muscle increased significantly(P<0.05).The expression of myod in the FP2.5 and FP5.0groups was up-regulated significantly(P<0.05),and the expression of mstn was downregulated significantly(P<0.05).The activity of GSH-PX was increased significantly(P<0.05).The expression of gsh-px 1b and gsh-px 4b in the FP5.0 group were significantly up-regulated(P<0.05).In summary,rice protein hydrolysate can replace 25% of fish meal,which can significantly promote the growth and metabolic function of Ictalurus punctatus.But when it replaces 75%,it has a significant inhibitory effect on growth,and may imbalance intestinal microbes and increase the abundance of harmful bacteria.Adding lysine to the 7.5% rice protein hydrolysate feed can effectively improve the growth performance of Ictalurus punctatus.Adding fish paste hydrolysate to the 5.0% rice protein hydrolysate feed,which can improve growth and significantly promote physical properties of muscle.