Effects of poly-β-hydroxybutyrate (PHB) on immune and digestive indicators in hepatopancreas of Litopenaeus vannamei

Litopenaeus vannamei of average weight of (5.66±0.14) g had been fed for 35 d with four different diets:0%, 1%, 3% and 5% poly-β-hydroxybutyrate (PHB) supplemented feed, and the immune and digestive indicators in hepatopancreas of shrimp were evaluated in this study.The results show that compared with the control group, the shrimps in 3% PHB group had higher total antioxidant capacity (T-AOC) and lysozyme (LSZ) activity (P < 0.05).The relative expression level of Toll gene increased but then decreased with increasing PHB content, and the expression levels in 1% and 3% PHB groups were higher than that in the control group significantly (P < 0.05).The relative expression levels of heat shock protein 70 (HSP70) gene in all three PHB treatment groups were higher than that in the control group significantly (P < 0.05).The amylase, pepsin and trypsin activities of 5% PHB group were significantly higher than those of the control group (P < 0.05), but the lipase activity showed no significant difference (P > 0.05).It is indicated that appropriate PHB content in diet can improve the immune and digestive abilities in hepatopancreas of shrimps significantly.