Effect of dietary supplement of inactivated Lactobacillus plantarum Ep-M17 on growth performance, immune response, disease resistance, and intestinal microbiota in Penaeus vannamei

Our previous study found that feeding with Lactobacillus plantarum Ep-M17 could effectively affect the growth performance, immune response, and gut microbiota of Penaeus vannamei. However, high temperature and pressure during feed pelletizing is the main problem that can lead to a decrease in the activity of probiotics or cause their inactivation. Further investigation needs to investigate whether inactivated Ep-M17 can exert similar effects as live Ep-M17. Therefore, we evaluated the effects of inactivated L. plantarum Ep-M17 on growth performance, immune response, disease resistance, and gut microbiota in P. vannamei. Results show that adding inactivated Ep-M17 to the feed also promoted body weight gain and increased relative immune protection in shrimp. Also, histological examination revealed that the administration of inactivated Ep-M17 led to improvements in the density and distribution of microvilli in the intestines and enhancements in the abundance of B and R cells in the hepatopancreas. Additionally, the inactivated Ep-M17 supplementation resulted in increased activity levels of nutrient immune-related enzymes in both the shrimp hepatopancreas and intestines. Moreover, it stimulated the expression of Lvlec, PEN-3a, Crustin, LGBP, Lysozyme, and proPo genes in both the hepatopancreas and intestines. Furthermore, the inactivated Ep-M17 also increased bacterial diversity in the gut of shrimp and promoted the abundance of specific flora, facilitating the host organism's metabolism and immunity to improve the disease resistance of shrimp. Therefore, supplementation of inactivated L. plantarum Ep-M17 in shrimp diets can exert similar effects as live L. plantarum Ep-M17 effectively improving growth performance, gut microbiota, immune response, and disease resistance in P. vannamei.