Antibiotics have been used worldwide to prevent, control and treat outbreaks of bacterial diseases in animal production. However, most antibiotics and their secondary metabolites cannot be absorbed and are then discharged into the aquatic environment, which might act as a severe threat to aquatic health. The present work evaluated whether dietary antibiotic-induced side effects in the shrimp could be improved by the dietary addition β-glucan in white shrimp (Litopenaeus vannamei) (average weight 0.37 ± 0.02 g). A 6-week feeding trial was conducted with four groups: control, 1g/kg β-glucan; 50mg/kg oxytetracycline (OTC) and 50mg/kg OTC with 1g/kg β-glucan (Mix). Parameters including growth performance, intestinal microbial composition, antioxidant capacity and non-specific immunity were determined.
The condition factor of L. vannamei in the Mix group was lower than those the other groups. The OTC group displayed higher SOD and CAT activities in the hepatopancreas than the β-glucan group. The MDA content in all groups showed no significant differences. The removal of low-quality reads and chimeras yielded a total of 1,690,040 clean sequences with intestinal contents and lengths ranging from 401 to 440bp (average 413 bp). Compared with the control group, the Observed_species index was significantly increased in the Mix group. The most
dominant phyla in the gut of all samples were
Proteobacteria, Bacteroidetes and Actinobacteria. Actinobacteria abundance was significantly greater in the OTC group compated with the groups without OTC, but the abundance of Proteobacteria and Bacteroidetes showed a totally different trend (Figure 1).