| Largemouth bass(Micropterus salmoides),commonly known as California bass,is an important freshwater farmed fish that has developed rapidly in recent years.However,at present,the commercial feed of the fish has problems of high cost and uneven quality,and frozen fish is used as bait in many cases,which restricts the development of green farming of the fish.This study used fishmeal and two kinds of blended protein(BPro1,BPro2)which made by mixing several terrestrial animal and plant proteins in different proportions as the protein source and fat powder as the fat source to produce two compound feeds(D1and D2)that the fishmeal content was 30% and the blended protein content was 48%.Their protein and fat content were 48.29% and 12.54%,48.90%,and 12.06%.Taking largemouth bass commercial feed(D0)and frozen fish(Df)as control groups,600 juvenile largemouth bass juveniles with an initial weight of 11.83 ± 0.12 g were selected and randomly divided into 4 groups,with 3 repetitions in each group.There were 50 fish in each repeat group,and the breeding experiment was carried out in round plastic buckets for 8 weeks.After the test,evaluate the growth performance,serum physiological and biochemical indicators,antioxidant index,muscle quality and nitrogen and phosphorus emission indicators of the fish fed to each feed group to evaluate the application effects and economic and environmental benefits of the two test compound feeds.The research results and conclusions are as follows:1.Effects of different diets on growth performance of M.salmoidesThere was no significant difference in WGR,SGR,PER,FC,SUR,FI,CF and VSI between D1,D2 and D0(P > 0.05);but the HSI of D2 was significantly lower than that of D1 and D0 groups(P < 0.05);The cost of fish feed per kg of weight gain of D1 and D2 groups was 11.08 and 10.69 yuan,respectively,which was 24.52% and 27.18% lower than the D0 group(14.68 yuan),42.28% and 44.35% lower than the Df group(19.20 yuan)(P <0.05).The results show that among the three groups fed with compound feed,the growth performance of the D1 and D2 groups is comparable to the D0 group,but the economic benefits are significantly better than the D0 group.2.Effects of different diets on serum biochemical indexes of M.salmoidesThere was no significant difference in HDL-C,TG content and T-CHO,GPT activity in fish serum of D1,D2 and D0 groups,LDL-C content and AKP activity in D1 and D2 groups,and GOT activity in D2 and D0 groups(P > 0.05);However,the GOT activity of D1 group and the LDL-C content of D1 and D2 groups were significantly lower than that of D0 group(P > 0.05);the AKP activity of D2 group was significantly lower than that of D0group(P < 0.05).The results show that the blood lipid index of the D1 and D2 groups is better than the D0 group,but the non-specific immunity of the D2 group is not as good as the D0 group.3.Effects of different diets on serum and liver antioxidant enzyme activity of M.salmoidesIn serum,there was no significant difference in SOD and CAT activity of fish in D1,D2 and D0 groups,MDA content in D1 and D0 groups(P > 0.05);but T-AOC activity in D2 group was significantly lower than that in D0 group(P < 0.05).In the liver,there was no significant difference in SOD,T-AOC activity and MDA content of fish in D1,D2 and D0groups(P > 0.05);But CAT activity in D2 group was significantly higher than that in D0group(P < 0.05).In summary,the antioxidant capacity of fish serum in D1 and D2 groups is comparable to that in D0 group;the antioxidant capacity of fish liver in D2 group is better than that in D0 group.4.Effects of different diets on muscle quality of M.salmoides4.1 Effects of different diets on proximate composition of M.salmoidesThere was no significant difference in the content of water,crude fat and crude ash in whole fish and muscle in D1,D2 and D0 groups(P > 0.05);but the crude protein content in D1 and D2 groups was significantly higher than that in D0 group(P < 0.05).The results show that D1 and D2 feeds help to increase the protein content of whole fish and muscle.4.2 Effects of different diets on fatty acids composition in muscle of juvenile M.salmoidesThere was no significant difference in ARA,EPA,DPA,DHA,SFA,n-3PUFA,n-6PUFA of fish muscles in D1,D2 and D0 groups(P > 0.05);but the MUFA content of D2 group was significantly higher than that of D0 group(P < 0.05).The results basically reflected the fatty acid composition of each group of feed.4.3 Effects of different diets on textural properties and edible quality of M.salmoidesThere was no significant difference in the hardness,chewability,adhesiveness,and cooked meat rate of fish muscles in D1,D2,and D0 groups(P > 0.05);however,the recovery of D1 and D2 groups,and the water retention rate of D1 group were significantly higher than D0 Group(P < 0.05);the elasticity of D1 group,the shear force of D1 and D2 group was significantly lower than that of D0 group(P < 0.05).The results showed that the fish muscles in groups D1 and D2 were comparable to those in group D0 in terms of texture and edible quality.5.Effects of different diets on nitrogen and phosphorus emissions of M.salmoidesThe total nitrogen and total phosphorus waste output of each weight gain of D1 and D2 groups was 50.78 and 53.02 g N,3.3 and 3.96 g P,respectively,which were significantly lower than the 63.76 g N and 9.89 g P of Df group;There was no significant difference with the D0 group(P > 0.05),but the total phosphorus waste output was significantly lower than that of the D0 group(P < 0.05).That is,the nitrogen and phosphorus emission indexes of the D1 and D2 groups are better than those of the D0 and Df groups.In summary,after feeding fish with commercial feeds and D1 and D2 group feeds which added with complex proteinand,their growth performance,serum biochemical indicators,and muscle quality indicators are not significantly different,but the economic and environmental benefits and liver anti-oxidation index of D2 group are the best.Therefore,the feed formulated with blended protein 2 has the characteristics of high efficiency,low cost and environmental protection,and has the potential for popularization and application. |
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