Effects Of Soybean Meal Replacement With Clostridium Autoethanogenum Protein On Growth Performance,Health Status,Muscle Quality And Safety Of Grass Carp(Ctenopharyngodon Idellus)

Soybean meal is one of the most commonly used plant protein sources in aquafeeds.In recent years,due to the continuous increase in its demand and cost and the shortage of resources,finding a sustainable alternative protein source has become an important task for the aquaculture industry.Single-cell proteins have attracted the attention of researchers because of their high protein content.For example,Clostridium autoethanogenum protein(CAP)is a high-quality protein isolated from fermentation broth after Clostridium autoethanogenum uses carbon monoxide in industrial steelmaking waste gas to produce bioethanol.Its production process has the characteristics of green,energy saving and environmental protection.Therefore,it is considered to be an ideal alternative protein source.Taking grass carp as the research object,this study comprehensively evaluated the effects of replacing soybean meal with Clostridium autoethanogenum protein gradient on its growth performance,health status,muscle quality and safety characteristics,in order to provide basic data for the rational replacement of soybean meal in aquatic feed and the rational use of Clostridium autoethanogenum protein.In this experiment,Soybean meal of 0%(CAP0),15%(CAP15),30%(CAP30),45%(CAP45),75%(CAP75)and 100%(CAP100)was replaced with Clostridium autoethanogenum protein to prepare six diets with equal nitrogen and lipids,and 360 grass carps with an average weight of 512.05 ± 1.20 g were fed for 90 days.During the feeding trail,the sampling and the analysis were carried out on the day 45 th as the mid-term and90 th days as the final determination respectively.The results showed that:(1)In terms of growth performance: Clostridium autoethanogenum protein had no significant effect on the final weight,specific growth rate,feed coefficient and body index of grass carp in the middle and end stages of the experiment compared with the control group(P > 0.05);(2)In terms of serum biochemical indicators,the mid-term test found that compared with the control group,the glutamic oxaloacetic transaminase activity of the CAP15 group was significantly decreased,and the triglyceride content was significantly increased(P < 0.05).The end-stage detection showed that the aspartate aminotransferase activity in the CAP75 group was significantly higher than that in the control group(P < 0.05),and the contents of glucose,total cholesterol and low-density cholesterol in the CAP100 group were significantly lower than those in the control group(P < 0.05);(3)The results of liver tissue sections showed that Clostridium autoethanogenum protein had no negative effect on the liver health status of fish in the middle and end stages of the test compared with the control group;(4)As far as the muscle quality is concerned,the mid-stage results found that compared with the control group,the replacement of soybean meal with Clostridium autoethanogenum protein did not affect the routine components of muscle,and the p H of muscle in CAP45 group increased significantly,while the cooking loss decreased(P <0.05).The skin color,muscle color,hardness,shear force,adhesion and adhesiveness of fish among the experimental group did not change significantly(P > 0.05);The cohesiveness,springiness and chewiness of the CAP100 group were significantly lower than those of the control group(P < 0.05).The end-stage detection showed that compared with the control group,the muscle crude protein content,total essential amino acids and total non-essential amino acids in the CAP30 and CAP45 groups were all the same significantly increased(P < 0.05),and the crude ash content of muscle in the CAP75 group was significantly increased(P < 0.05);the muscle springiness,adhesiveness,chewiness and cohesiveness of CAP30 group and CAP100 group were significantly improved(P < 0.05),and the muscle tenderness,sarcomere length and inosinic acid content of CAP100 group was significantly improved(P < 0.05),while the content of volatile compounds in muscle was reduced(P < 0.05);CAP15 group could increase the brightness of grass carp abdomen and reduce the yellowness(P < 0.05),but had no effect on muscle color(P > 0.05);(5)In terms of safety characteristics,Clostridium autoethanogenum protein had no cause for the accumulation of copper,arsenic,cadmium and other heavy metals in grass carp muscle,so it would not have a negative impact on its safety characteristics.In summary,the present studies have shown that Clostridium autoethanogenum protein could be used completely to replace soybean meal(24%)in grass carp diets,that is,adding 12.75% of Clostridium autoethanogenum protein will not only have no negative impact on the growth performance,health status and safety performance of grass carp,but also could improve the muscle quality of grass carp.