| The growth and immune function were determined through feeding Hybrid tilapia,Oreochromis niloticus×O. aureus on different Coriolus versicolor polysaccharide levelsof 0g/kg,0.5g/kg,1.0g/kg,1.5g/kg,2.0g/kg,2.5g/kg.Part one: The experiment was conducted to determine the effect of dietarypolysaccharide levels on growth and the activity of the protease, lipase and amylase inforegut, midgut, hindgut, stomach and hepatopancreas of hybrid tilapia (Initial meanweight: 9.0±1.0g) after 56 days. Apparent digestibility coefficients of dry matter, proteinand lipid were obtained of dietary polysaccharide levels. The main results weresummarized as follows:1. The dose of 0.5g/kg-1.5g/kg polysaccharide enhanced weight growth ratio (WGR),specific growth ratio (SGR), feed conversion efficiency (FCE), protein conversionefficiency (PCE) and condition factor (CF), decreased feed conversion ratio (FCR) and feedrate (FR). Especially, the effect of 0.5g/kg polysacchadde was significant higher thancontrol group. Dose of 2.5g/kg polysaccharide resulted in worse growth responses. Therewas no significant difference of back-muscle composition (crude protein, crude fat, ashand moisture) and livability among groups.2. The dose of 1.0g/kg polysaccharide enhanced the activity of the protease inforegut, midgut and stomach. The activity of lipase were depressed by feeding diets withpolysaccharide, dietary 2.5g/kg polysaccharide made midgut, stomach andhepatopancreas activity of lipase significant lower than control group. The activity ofamylase in intestinal, hepatopancreas and stomach were no significant difference amonggroups.3. Dietary different polysaccharide levels can influence the apparent digestibilitycoefficient of hybrid tilapia, the dry matter digestibility of the test groups were slightlyhigher than the control group, but no significantly. Protein digestibility of 0.5g/kg and1.0g/kg were significantly higher than the control group, and lipid digestibility taperedwith adding polysaccharide concentrations.Part two: The phagocytic activity of leukocytes, lysozyme activity in serum and theserum hemolytic complement activity of hybrid tilapia (Initial mean weight:100.0g±10.0g) were measured at 0, 7, 14, 21 and 28 days after feeding, and hybrid tilapiasurvival rate was also recorded after challenge with live A. hydrophila. The main resultswere summarized as follows: 1. The phagocytic activity of leukocytes, serum lysozyme activity and serumhemolytic complement activity of hybrid tilapia were markedly enhanced by dietary0.5g/kg and 1.0g/kg polysaccharide, especially, the effect of 1.0g/kg polysacchafide wasbest. During the experiment, polysaccharide made the immune level of test groups climbat first, and then drop. With low additive concentrations (0.5g/kg-1.0g/kg) could increasethe immune function of hybrid tilapia for a long term; as concentration increased(=1.5g/kg), immune parameters enhanced for a short term.2. Polysaccharide could improve the survival rate of hybrid tilapia after challengedwith live A. hydrophiIa. The survival rate of 1.0g/kg polysaccharide was higher thanothers.In this review, 0.5g/kg-1.0g/kg of polysaccharide was recommended for improvingthe growth and enhanced the immunity as well as increased disease resistance of hybridtilapia.
|
PDF Full Text Request