| Purpose: This experiment was conducted to investigate the effect of replacement of fish meal(FM)with fermented silkworm pupae meal(FSPM)on growth performance, body composition, intestinal protease activity and health status in juvenile mirror carp(Cyprinus carpio var. specularis) and to test the potential of FSPM as an optimistic protein source for mirror carp diets.Methods: The FSPM was prepared under solid state fermentation and analyzed by SDS-PAGE to estimate a profile of protein sizes. Afterwards, 0%, 25%, 50%, 75%, 100% of fish meal protein were substituted by FSPM to formulate five isonitrogenous and isolipidic diets. The experimental fish with same size(initial average weight, 9.70±1.02 g) were randomly allotted to five groups with triplicate of tanks(18 fish per tank).At the end of the feeding trial, all of the fish were fasted for 24 h and anesthetized with MS222(100 mg L). The weight of the body and the viscera, the length of body and intestine were measured. The blood, muscle and hepatopancreas were rapidly sampled. The growth performance, feed utilization, ADCs, intestinal digestible enzymic activities, body composition, fatty acid composition of the muscle and hepatopancreas, serum biochemical indices and immune gene expression of the hepatopancreas were measured and analyzed.Results: SDS-PAGE analysis showed that the protein components of the FSPM appeared to have relatively small molecular sizes compared with the unfermented silkworm pupae meal. After a 58-day feeding trial, the final weight, special growth rate(SGR), feed conversion ratio(FCR) and protein efficiency ratio(PER) of fish were decreased with increasing FSPM levels, and significant differences were foundin fish fed with 50% replacement level(P<0.05). The apparent digestibility coefficient of dry matter, crude protein and crude fat were decreased with the ration level, but no significant differences were found among the treatments(P>0.05), as well as the intestinal trypsase and lipase activity(P>0.05). The crude fat of whole body and muscle were significantly decreased at over 50% replacement level(P<0.05), while the moisture, crude protein and ash content showed no differences(P>0.05). With increasing fish meal replacement level, the contents of C18:3n-6, C18:3n-3 and C22:4n-6 in muscle were significant increased(P<0.05), while the content of C20:1n-9, C20:5n-3, C22:6n-3 and n-3 PUFA were significantly decreased(P<0.05). The contents of C16:0, C18:3n-3 and SFA in hepatopancreas were significantly increased with the replacement level(P<0.05), however, the content of C14:0, C16:1n-7, C18:1n-9, C20:5n-3 and MUFA were significant decreased(P<0.05).No significant differences of the hepatosomatic index(HI), kidney index(KI) and gallbladder somatic index(GBSI) were found among the treatments(P>0.05), while the spleen indexes(SI) were significant increased at 50% and 75% replacement levels compared with the other levels(P<0.05). The contents of serum TG, LDL-c and MDA were significantly decreased with ration level(P<0.05), and so were the serum SOD activities(P<0.05). When replacing over 75%, the expression of hepatic TNF-α1 and IL-6 were significantly increased compared with other treatments.Conclusion: It is possible to replace 25% of the dietary FM protein with FSPM without affecting growth performance, whereas supplementation with 50% or more FSPM may adversely affect growth performance and the health status of mirror carp. |
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