Effects of dietary stickwater hydrolysate and plant essential oils on growth performance,immunity,digestive enzyme activity and TOR related gene expression of juvenile turbot Scophthalmus maximus
1.Shandong Key Laboratory of Marine Ecological Restoration,Shandong Marine Fishery Feed Engineering Technology Research Center,Shandong Marine Resources and Envionment Research Institute,Yantai 264006,China;2.Shanghai Collaborative Innovation for Aquatic Animal Genetics and Breeding,Centre for Research on Environmental Ecology and Fish Nutrion，Ministry of Agriculture and Rural Affairs,National Demonstration Center for Experimental Fisheries Science Education,Shanghai Ocean University,Shanghai 201306,China
Abstract: The purpose of this experiment is to investigate the dietary stickwater hydrolysate (SWH) and plant essential oil on growth performance,immunity,digestive enzyme activity and TOR related gene expression of juvenile turbot Scophthalmusmaximus fed low fish meal diets.Juvenile turbot with initial body weight of 37.67 g were reared in a closed water circulating system and fed diets containing 50% fish meal (D1,positive control),and containing 30% fish meal (D2,negative control),and 30% fish meal diets supplemented with 1% SWH (D3),0.02% plant essential oil (D4),and 1% SWH+0.02% plant essential oil (D5) with triplication at water temperature of (16±1)℃ for 8 weeks.The results showed that there were significant increase in weight gain rate,specific growth rate and protein efficiency ratio and significant decrease in feed conversion ratio in the turbot in D3 group (P<0.05).The maximal activities of serum lysozyme was observed in the turbot in D5 group (P<0.05),significantly higher than that in the D2 group (P<0.05),without significant difference from D1 group(P>0.05).The turbot in D5 group had the minimal C3 content,significantly lower than that in other 4 groups(P<0.05).The maximal intestinal trypsin activity was found in the turbot juveniles in D3 group (P<0.05),significantly higher than that in the D2 group(P<0.05),without significant difference from D1 group (P>0.05).The maximal TOR mRNA expression level was observed in liver of fish in D3 group,significantly higher than that in the D2 and D1 groups (P<0.05),with an opposite trend in 4EBP1 and 4EBP2 mRNA expression levels (P<0.05).There was significantly lower cumulative mortality of juveniles exposed to Vibrioanguillarum infection at a dose of 7.94×105 CFU/g for 48 h in D4 and D5 groups than that in D2 group (P<0.05).It can be concluded that supplementation of 1% SWH led to significantly enhance the growth performance,trypsin activity,liver TOR related gene expression level of turbot,and that 0.02% plant essential oil to significantly enhance the ability of fish to resist V.anguillarum infection.However,the combination of 1% SWH and plant essential oil does not result in good effect instead of low weight gain,the mechanism of their interaction needs further research.
2022, Vol. 37 
