Effects of Lactobacillus pentosus HC-2 on the growth performance, intestinal morphology, immune-related genes and intestinal microbiota of Penaeus vannamei affected by aflatoxin B1

Lactobacillus pentosus HC-2 is a lactobacillus previous isolated and identified from aquatic animals (such as the goby, Acanthogobius hasta), which has shown a positive effect on growth and disease resistance in the Pacific white shrimp, Penaeus vannamei. Aflatoxin B1 (AFB1) is a highly carcinogenic and teratogenic toxin found in moldy feeds. This study aims to investigate the positive effect of L. pentosus on protecting the intestine of P. vannamei affected by AFB1 toxicity. Shrimp were respectively fed with formulated feed containing AFB1 (500 mu g/kg), AFB1 (500 mu g/kg) + L. pentosus HC-2 (5 x 10(8) CFU/g feed), and a basal commercial diet (Control group). After feeding for 6 weeks, the survival rate (AFB1 group: 37%, AFB1 + L. pentosus HC-2 group: 49%,Control group:61%) and the percent weight gain (AFB1 group: 98.28%, AFB1 + L. pentosus HC-2 group: 112.40%,Control group:111.27%) in the AFB1 + L. pentosus HC-2 group were higher than the AFB1 group. The intestinal morphology of the AFB1 + L. pentosus HC-2 group was more complete than that of the AFB1 group. The relative expression of immune-related genes including Rab, GST, mucin-like-PM, Dorsal, Relish and Pro-PO was detected. Expression in the experimental group significantly decreased compared with the control group, while the expression levels of immune genes (Rab, GST, mucin-like-PM, Dorsal and Pro-PO) in AFB1 + L. pentosus HC-2 group was higher than the AFB1 group. Intestinal microbiota analysis demonstrated that the community structure of intestinal microbiota was markedly different between the control group and experimental group. Comparing different genera of bacteria, the abundance of Proteobacteria in the AFB1 + L. pentosus HC-2 group increased significantly compared with the control group, while the abundance of Firmicutes and Bacteroidetes decreased. These results indicated that L. pentosus HC-2 had a positive effect on the growth performance and resistance of P. vannamei affected by AFB1 according to regulate the structure of intestinal flora. In breeding practice, probiotics can be used to reduce the harm of aflatoxin. This may be related to the probiotic's contribution to maintaining the structural integrity of the intestinal mucosa, promoting the expression of immune related genes and regulating the composition of intestinal microflora.