Role of dietary Schizochytrium sp. in improving disease resistance of zebrafish through metabolic and microbial analysis

Abstract Background As an essential nutrient for farmed fish, the fish oil from wild fish has been partly replaced by vegetable ingredients to prevent overfishing. Schizochytrium sp., a type of marine microalgae, is considered as a promising alternative to fish oil for improving growth and fatty acid profile in fish. However, there lacks a comprehensive understanding of disease resistance on microalgae supplementation of fish. In the present study, to understand the pathogen-resistant mechanisms of diets enriched with microalgae, the effects of dietary Schizochytrium sp. on the intestine microbial and metabolic profile of zebrafish were investigated. Results The challenge trial with Edwardsiella piscicida showed that 120 g/kg Schizochytrium sp. supplementation had a significantly higher survival rate of zebrafish . Additionally, higher goblet cell density was observed in zebrafish fed with Schizochytrium sp. Metabolomic analysis of humoral fluids indicated that the diet supplemented with Schizochytrium sp. boosted the TCA cycle, energy supply, taurine metabolism, and L-serine metabolism, whereas decreased cholesterol metabolism in zebrafish. The microbiome analysis revealed that a 120 g/kg Schizochytrium sp. supplemented diet could remarkably increase the abundance of beneficial bacteria (i.e., Lactobacillus , Dorea , Butyricicoccus , and Pseudoxanthomonas ), and reduce several potential pathogens (i.e., Flavobacterium, Pseudomonas, Citrobacter, and Mycoplasmas ). Combined omics analysis indicated that some Dorea and Butyricicoccus species might be candidate probiotics with disease resistance. Conclusions Dietary supplement of Schizochytrium sp. could improve the survival rate of zebrafish when infected with Edwardsiella piscicida . It further revealed that Schizochytrium sp. as feed additive had the potential to improve metabolism and the intestine health by dual-omics analysis, and thus enhance disease resistance of zebrafish. Our research provides a novel insight into developing the fundamental understanding of disease resistance in aquatic animals fed with microalgae. Moreover, this experiment shed substantial light on the screening of probiotic candidates with immunomodulatory properties.