Effect Of Fish Meal Replaced By Blended Plant Proteins On Growth And Immunity Of Juvenile Hybrid Sturgeon

Protein is the most expensive ingredient in sturgeon feed, and fish meal remains the prominent protein source because of its well-balanced amino acid profile,digestible energy, vitamins and minerals. However, due to the limited supply and high cost of fish meal, there is an increasing need to replace this ingredient with less expensive protein from plant sources(e.g., soybean meal, cottonseed meal or rapeseed meal) in feeds. Considering differences in antinutritional factors, essential amino acid composition and availability in supply, it has been proposed to use the mixture of plant ingredients as a substitute of fish meal in aquaculture diets. However, the mixed use of soybean meal, cottonseed meal and rapeseed meal has not been fed to any sturgeon species. Therefore, specific strategies and techniques to improve the use of soybean meal, cottonseed meal and rapeseed meal in the sturgeon' feeds are discussed in this paper. The results can be briefly summarized as follows:1. Effect of fish meal replaced by blended plant protein on growth, feed utilization and muscle composition of juvenile hybrid sturgeonThis trial was conducted to evaluate the effect of replacing fish meal with blend protein(soybean meal(SBM): rapeseed meal(RM): cottonseed meal(CSM) =5:6:7)on growth, feed utilization and muscle composition in juvenile hybrid sturgeon(Acipenser baerii?×Acipenser schrenckii?). Five isonitrogenous and isoenergetic diets were formulated to replace 0(FM60), 25%(FM45), 50%(FM30),75%(FM15) and 100%(FM0) of fish meal, respectively. Those diets were used mixture oil(fish oil: soybean oil) as the source of fat, microcrystalline cellulose as filler and carboxymethyl cellulose as binder. All fish were fed for 84 days. Results showed that:(1) There were no significant differences of final body weight, weight gain, specific growth rate and survival between FM60, FM45, FM30 and FM15(P >0.05).(2) No significant differences of daily feed intake were found in each group(P > 0.05). The feed conversion ratio of group FM60 was significantly lower than that of FM0(P < 0.05). The protein efficiency ratio, protein retention and energy retention of group FM60 were significantly higher than that of group FM15 and FM0(P < 0.05), but no significant differences were found between FM60, FM45 and FM30(P > 0.05).(3)No significant differences in activities of amylase, lipase and trypsin were found between FM60, FM45 and FM30(P > 0.05).(4) The apparent digestibility of dry matter, protein, lipid, gross energy and GAA apparent digestibility between group FM60, FM45 and FM30 were not significantly different(P > 0.05),but were significantly higher than that of FM15 and FM0(P < 0.05).(5) The crude protein and crude lipid of muscle in fish fed FM15 and FM0 diets were significantly lower than of fish fed FM60 diet(P < 0.05). The levels of free gossypol in muscle significantly increased with the increase of cottonseed meal. The levels of TAA in muscle of each group were about 80%~82%. No significant differences of the levels of EAA,NEAA in muscle were found between FM60, FM45 and FM30, except for threonine(P > 0.05). In conclusion, the maximum replacement ratio of fish meal by a mixture of SBM, RM and CSM was 50% based on the results of growth performance,food utilization and muscle composition.2. Effect of fish meal replaced by blended plant protein on ammonia excretion rate, oxygen consumption rate and activities of transaminase of juvenile hybrid sturgeonResults showed that:(1) The levels of ammonia-N excretion rate of fish in group FM45 and FM30 were significantly lower than that of fish in group FM60, FM15 and FM0(P < 0.05). The level of oxygen consumption rate of fish in group FM60 was significantly lower than that of fish in the other groups. The O:N ratio indicated that protein was increasingly used as an energy substrate when fish meal was replaced by plant proteins.(2) Activities of GPT and GOT in FM15 and FM0 were significantly lower than that in FM60, FM45 and FM30. In conclusion, juvenile hybrid sturgeon anabolism reduced and catabolism enhanced when plant protein reached 50%.3. Effect of fish meal replaced by blended plant protein on immunity and express of HSP70 mRNA of juvenile hybrid sturgeonResults showed that:(1) Activities of serum LSZ, serum SOD, and liver SOD in group FM60 were significantly higher than that of FM15 and FM0(P < 0.05). The levels of serum MDA in group FM30 and FM15 were significantly higher than that of the other groups(P < 0.05). The levels of liver MDA and the activities of serum GPT,GOT in group FM0 were significantly higher than that of the other groups(P < 0.05).(2) Use ?-actin as internal reference, the expression of HSP70 of liver in group FM30 and FM15 were significantly higher than that of the other groups(P < 0.05). The expression of HSP70 of intestines in group FM60, FM45 and FM30 were not significantly different(P > 0.05), and were significantly lower than that of group FM15 and FM0. In conclusion, replaced fish meal by blended plant should not higher than 50% when consider the immunity of juvenile hybrid sturgeon.4. Effect of fish meal replaced by blended plant protein on intestines and liver morphologyResults showed that: Intestines chorion of group FM60 showed structural integrity and distinct. Intestinal structure damaged with the increase level of plant proteins. Serious vacuolization, villi falled off and ruptured were found of intestinal structure when the replaceing levels were more than 50%. The phenomenon of vacuolization in liver cytoplasm, cell nucleus dissolved and disappeared, cell boundary unclear in liver of fish were found in group FM30, FM15 and FM0. This study indicates that no more that 50% of FM can be replaced with a mixture of soybean meal, rapeseed meal and cottonseed meal in the diet of juvenile hybrid sturgeon without compromising intestines and liver morphology.