| Two experiments were conducted to investigate the effect of replacement of fishmeal by soybean meal and dietary supplement of taurine on juvenile topmouth culter(Culter alburnus)growth performance, body composition and serum biochemical indices, and feeding strategy on growth performance and digestive enzymes activity of juvenile topmouth culter. The main results are summarized as follows:1 〠A 4×2 two-factorial experiment was conducted to valuate the effects of replacement of dietary fishmeal by soybean meal(0.00%, 20.0%, 35.0%, 50.0%) and dietary supplementation of taurine(0.00%, 1.00%) on the growth, body composition and blood biochemical indices of juvenile topmouth culter. Fish in 8 groups(3 replicates per group and 30 fish per replicate) were fed eight iso-nitrogenous and iso-lipidic experimental diets with D1~D8(crude protein 45.43% ± 0.80%; crude lipid 9.20% ± 0.44%). The results showed as follows: growth performance of juvenile topmouth culter was not affected by the replacement of fishmeal by soybean meal and dietary supplement of taurine(P > 0.05). Regardless of dietary supplement of taurine, higher replacement of fishmeal by soybean meal decreased the body protein contents and body lipid contents significantly(P < 0.05). The levels of alanine aminotransferase(ALT), aspartate aminotransferase(AST), alkaline phosphatase(AKP) and triacylglyceride(TG) in serum obviously increased with the increasing replacement of fishmeal by soybean meal(P < 0.05), while the change of total cholesterol(TC), high density lipoprotein cholesterin(HDL-C) and low density lipoprotein cholesterin showed an opposite trend. Compared with the nonsupplemented groups, dietary supplement of taurine significantly decreased body lipid contents(P < 0.05) and led to obviously lower levels of AST, ALT, AKP, TG, TC, HDL-C and LDL-C(P < 0.05). Significant interactions between replacement of dietary fishmeal by soybean meal and taurine were observed on the condition factor(CF), IPF, Visceerosomatic index(VSI), AST, AKP, TG, TC, HDL-C, LDL-C(P < 0.05). As a result, in the present study, the optimum replacement level of fish meal by soybean meal was 35%. Besides, dietaty supplementation of 1% taurine improved the growth performance of juvenile topmouth culter.2 〠THSI experiment was conducted to study the effects of different feeding frequencies( F1, once daily; F2, twice daily; F3, three times daily; F4, four times daily) and feeding levels(S1, 100% satiation; S2, 85% satiation; S3, 70% satiation; S4, 55% satiation) on growth performance and digestive enzyme activities of juvenile topmouth culter, Culter alburnus, reared in net cages which placed in an earthen pond. The results showed tht the final body weight(FBW), weight gain rate(WGR) and specific growth rate(SGR) decreased significantly with the feeding frequency increase(P < 0.05) and the values of group F1 were significantly greater than groups F3, F4(P < 0.05). The feeding rate(FR) and feed conversion ratio(FCR) increased significantly with the feeding frequency increase(P < 0.05). The FBW, WGR, SGR and FCR decreased significantly with the feeding level decrease(P < 0.05) and the values of group S1 were significantly greater than groups S2, S3 and S4(P < 0.05). Feeding frequency significantly affected the protease, lipase activities and amylase activity in intestine and hepatopancreas(P < 0.05). Feeding level significantly affected all the digestive enzyme activities(P < 0.05). The values of digestive enzyme activities of group S4 were significantly greater than groups S1, S2 and S3(P < 0.05). It is concluded that, the optimal feeding frequency and feeding level for juvenile topmouth culter(1.34 ± 0.03 g) are once daily and 100% satiation under the experimental conditions based on the best SGR. |
