Effects of dietary poly-beta-hyroxybutyrate supplementation on the growth, immune response and intestinal microbiota of soiny mullet (Liza haematocheila)

Authors: QIAO, GUO - Yancheng Institute Of Technology; XU, CHEN - Yancheng Institute Of Technology; SUN, QIRUI - Yancheng Institute Of Technology; Xu, Dehai; ZHANG, MINGMING - Yancheng Institute Of Technology; CHEN, PENG - Yancheng Institute Of Technology; LI, QIANG - Yancheng Institute Of Technology

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2019
Publication Date: 5/20/2019
Citation: Qiao, G., Xu, C., Sun, Q., Xu, D., Zhang, M., Chen, P., Li, Q. 2019. Effects of dietary poly-beta-hyroxybutyrate supplementation on the growth, immune response and intestinal microbiota of soiny mullet (Liza haematocheila). Fish and Shellfish Immunology. 91:251-263.

Interpretive Summary: Diseases have seriously restricted the culture of soiny mullet, an important economic fish species in Asian aquaculture. Alternative methods are needed to prevent the infectious diseases, such as using novel immunostimulant poly-ß-hydroxybutyrate (PHB). The object was to evaluate the effects of dietary PHB supplementation on the growth, antioxidant enzymes activity, immune-related genes expression and intestinal microbiota in soiny mullet. Soiny mullet fed PHB diets at the concentration of 2% for 30 days showed better growth performance, higher antioxidant enzymes activity, higher diversity of intestinal micro-organisms and higher immune-related genes expression. The study results provided valuable information on immunostimulant for disease prevention in soiny mullet culture, determined the optimal feeding concentration of PHB supplementation and feeding period, and explored the mechanism of PHB primarily in view of intestinal microbiota since gut bacterial diversity can affect the health and immune system of fish. The study results will be beneficial for the soiny mullet aquaculture.

Technical Abstract: Soiny mullet (Liza haematocheila) is an important economic fish species in Asian aquaculture, but stress and diseases have seriously restricted its culture. Alternative methods are needed to prevent the infectious diseases, such as using novel immunostimulant poly-ß-hydroxybutyrate (PHB). The present study aimed to evaluate the effects of dietary PHB supplementation on the growth, antioxidant enzymes activity, immune-related genes expression and intestinal microbiota in soiny mullet. The fish was fed for 30 or 60 days with six diets at different PHB supplementation of 0, 0.5, 1, 2, 4 and 8%, named as groups P0, P0.5, P1, P2, P4 and P8. The results showed that the weight gain and specific growth rate of fish in P2 and P0.5 groups were significantly higher than those of fish in P0 at the end of 30 and 60 days, respectively (P<0.05). The antioxidant enzymes activity of catalase and superoxide dismutase in serum were significantly increased in P0.5/P1/P2 groups after 30 days compared with P0 group. The expression levels of penicillin-binding protein A and interleukin-8 analyzed by qRT-PCR were significantly up-regulated in P2 and P4 groups compared to those in P0/P0.5/P1/P8 groups after 30-day treatment. The expression levels of aldehyde oxidase and major histocompatibility complex class II were significantly up-regulated in P2 group compared to those in P0 group. Intestinal microbiota analysis by Illumina sequencing showed that Chao1 and Simpson’s indexes in P2 group (224.0 and 0.17) were higher than those in P0 group (207.67 and 0.12), indicating that the diversity of intestinal microbiota in P2 was higher than P0. The top four phyla in PHB supplementation and control groups were Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Dietary supplementation of PHB increased the abundance of Firmicutes and Bacteroidetes phyla, while reduced the abundance of phylum Proteobacteria. At the genus level, Bacillus, Lactococcus and Achromobacter were the top three genera in the gut of soiny mullet in both P0 and P2 groups. In conclusion, soiny mullet fed with 2% PHB supplemental diets for 30 days showed better growth performance, higher antioxidant enzymes activity and immune-related genes expression.