Effects Of Dietary Probiotics Or/and Prebiotics On Growth, Survival, Activities Of Digestive Enzymes And Stress Resistance Of Large Yellow Croaker (Pseudosciaena Crocea) Larvae

Isoproteic and isolipidic experimental micro-diets with graded levels probiotics or/and prebiotics (yeast cell wall polysaccharide) were fed to large yellow croaker larvae (15days post hatch, initial body weight 2.75±0.31mg) for 30d to investigate the effects on growth, survival, activities of digestive enzymes and stress resistance of the larvae.Experiment 1:Four experimental micro-diets supplemented with 0.00% (control),0.20%,0.50% and 1.00% compound probiotics Xiale333(Bacillus Subtilis, lactobacillus and Arthrobacter@109cfu/g as primary effective ingredients) were fed to the larvae. Results showed that the specific growth rate (SGR) had an increasing trend with increasing Xiale333, but no significant difference was observed among dietary treatments (P>0.05). Significantly improved survival were observed in larvae fed diets with supplementation of compound probiotics, and survival in larvae fed the diets with 0.20%,0.50% and 1.00% supplementation were significantly higher than that of control group (P<0.05). The challenge experiment showed an analogous trend as that of survival, the supplementation of compound probiotics significantly elongated the half-lethal time of larvae when challenged with high temperature (P<0.05), but there were no remarkable difference among 0.20%,0.50% and 1.00% supplementation groups (P>0.05). There were no significant difference in activities of amylase and trypsin in intestinal or pancreatic segments among fish fed different diets (P>0.05). The activities of alkaline phosphatase in intestinal segments of larvae in 0.20% treated group were significantly higher than that of the control group, indicating that compound probiotics supplements promoted the mature of digestive gut of large yellow croaker larvae. Results of the present study indicted that compound probiotics Xiale333 could promote growth, significantly improve survival and stress resistance and speed the development of digestive tract of large yellow croaker larvae.Experiment 2:Four experimental micro-diets with graded levels (0.00% (control),0.25%,0.50% and 1.00%) of yeast cell wall polysaccharide (YCWP, mainly includingβ-glucans and mannan oligosaccharides (MOS)) were fed to large yellow croaker larvae. Results indicated that 0.25% YCWP supplementation significantly enhanced the growth (P<0.05), whereas higher YCWP doses (0.50% and 1.00%) induced the declined growth compared with 0.25% YCWP group (P>0.05). The supplements of YCWP significantly increased the survival of larvae (P<0.05). However, there were no significant differences in survival among YCWP supplemented groups (P>0.05). The YCWP supplemented groups were recorded with the prolonged half-lethal time in response to high temperature (32℃), which proved higher tolerance resistance. The activities of digestive enzymes including trypsin, amylase, aminopeptidase N (AN) and alkaline phosphatase (AP) activities were not significantly different among dietary treatments (P>0.05). In conclusion, YCWP administrations exhibited great enhancement on growth, survival and tolerance resistance of large yellow croaker larvae except activities of digestive enzymes.Experiment 3:Four micro-diets (control diet, control diet with 0.20% compound probiotics (Xiale333, Bacilius Subtilis, lactobacillus and Arthrobacter @109cfu/g as primary effective ingredients) or/and 0.25% yeast cell wall polysaccharide (YCWP, mainly includingβ-glucans and mannan oligosaccharides (MOS) supplements)) were fed to large yellow croaker larvae. The results showed that the specific growth rate (SGR) had an increasing trend with supplementation of dietary probiotics (P>0.05),0.25%YCWP supplementation significantly enhanced the SGR of larvae (P<0.05). However, there were no significant differences in SGR among 0.20% Probiotics group,0.25% YCWP group and 0.20% Probiotic + 0.25% YCWP group (P>0.05), but there was significant interaction between probiotics and yeast cell wall pojysaccharide (P<0.05). Survival and half-lethal time to high temperature tolerance (32℃) of larvae were significantly higher in 0.20% Probiotics group,0.25% YCWP group and 0.20 Probiotics + 0.25% YCWP group compared with the control group (P<0.05), but there were no significant differences among the three treated groups, and interaction on survival and tolerance resistance were also observed. There were no significant differences in activities of amylase and trypsin in intestinal or pancreatic segments, aminopeptidase N (AN) and alkaline phosphatase (AP) in intestinal segments among fish fed different diets (P>0.05). In conclusion, dietary probiotics or/and yeast cell wall polysaccharide enhanced the growth, and improved the survival and tolerance resistance of large yellow croaker larvae, except activities of digestive enzymes. In this experiment, probiotics and yeast cell wall polysaccharide performed interaction effects on growth, survival and tolerance resistance of lavae.