Effects of fermented soybean meal and guanosine 5'-monophosphate on growth, intestinal health and anti-stress capability of Penaeus vannamei in low fish meal diet

Substitution of fishmeal by plant protein source has been one of the most concerned issues in aquaculture. The present study aimed to evaluate the replacement of fishmeal by fermented soybean meal (FSM) and supplementation of nucleotide, guanosine 5′-monophosphate (5′-GMP), on growth, intestinal health and anti-stress capability in Penaeus vannamei. Six diets were formulated to contain three replacement levels of fish meal by FSM (0, 22.22% and 44.44%) with or without 5′-GMP (0.1%). The feeding trial lasted for 8 weeks, followed by the hypoxia exposure. The results indicated that 44.44% of fishmeal substituted by FSM did not have negative effects on growth and digestive enzymes activities in shrimp, while it significantly affected intestinal micromorphology by decreasing fold height, enterocyte height and microvillus height. 22.22% of Fishmeal substituted by FSM had higher genes expression of target of tor, s6k and 4ebp1 suggesting the potential improvement in growth. Application of FSM influenced intestinal microbiota of shrimp with the changes in microbiota composition, community diversity and richness. Metabolites and enzymes associated with stress response including MDA, LD, SOD, T-AOC, GSH and GSH-PX were all markedly increased after hypoxia stimulus, and SOD, T-AOC and GSH-PX was significant higher in the shrimps fed without 5′-GMP in high fishmeal diet. Lgbp and hsp70 mRNA level were also higher in the shrimp after hypoxia stimulus especially fed with 5′-GMP in low fishmeal diet, while sp and pe were lower expressed in the shrimps after hypoxia stimulus. Finally, our results determined that FSM had a fishmeal sparing effect for the diet of P. vannamei, and the supplementation of 5′-GMP in the diet slightly benefited growth, gut health and anti-stress capacity for P. vannamei.