Effect of different nutrient sources on the growth, disease resistance, and intestinal health of Exopalaemon carinicauda infected by Enterocytozoon hepatopenaei

The ridgetail white shrimp, Exopalaemon carinicauda, is an economically important mariculture crustacean species in China. Nevertheless, during cultivation, it is often infected with Enterocytozoon hepatopenaei (EHP). Aiming to alleviate the disordered host nutritional metabolism and the reduced immune defense caused by E. hepatopenaei infection, in this study, we formulated and evaluated feeds with three protein levels (30 %, 40 %, and 50 %) and live feed (Artemia, Daphnia, and Hermetia illucens).1）The baits from the different nutrient sources were systematically analyzed for their effects on the growth performance of E. hepatopenaei, and the intestinal tissue structure and microbiota of E. carinicauda infected with E. hepatopenaei. The results showed that: (1) At 28 days after EHP infection, the ridgetail white prawn (Exopalaemon carinicauda) in the 50 % protein group achieved the maximum weight gain rate (WGR) and specific growth rate (SGR), along with the lowest feed conversion ratio (FCR) (WGR: 30.93 %, SGR: 0.96 %/d, FCR: 4.13). Among the biological baits, Daphnia yielded the highest WGR and SGR, as well as the lowest FCR (WGR: 29.27 %, SGR: 0.92 %/d, FCR: 5.58). (2) The loading of E. hepatopenaei in each group showed a trend of first increasing and then decreasing with a prolongation of infection time, indicating that each group had a certain inhibitory effect on the E. hepatopenaei load, and Daphnia had the greatest inhibitory effect. (3) Analysis of the intestinal microbiota showed that the 50 % protein group and the Daphnia group were mainly comprised of beneficial bacteria (e.g., Acinetobacter and Cupriavidus genera), and their functions were enriched in disease-resistant-related pathways such as vitamin synthesis and selenium metabolism. Among them, 50 % of the protein group and the Daphnia group exhibited the highest intestinal villi height, along with a favorable muscular layer thickness. The mechanism by which baits from different nutrient sources regulate E. hepatopenaei infection was demonstrated to be through the “nutrition-immunity-microbiota” axis. Overall, the 50 % protein feed and Daphnia bait were found to significantly improve the growth performance of infected shrimp, inhibit the E. hepatopenaei load, and improve the intestinal microecology, suggesting their potential use as functional baits against E. hepatopenaei infection. These results also provide a theoretical basis for the prevention and control of E. hepatopenaei diseases and the development of other functional baits in aquaculture.