Dietary yeast culture facilitates the growth, immune response, digestive enzyme activity, intestinal microbiota and disease resistance against <i>Vibrio harveyi</i> of hybrid grouper ( <i>Epinephelus fuscoguttatus</i> ♀ × <i>Epinephelus lanceolatus</i> ♂)

Abstract

The present study aimed to investigate the effect of yeast culture (YC) supplementation at different levels (0%, 2% and 4%) on the growth, immune response, digestive enzyme activity, intestinal morphology and microbiota of hybrid grouper. After 56 days feeding trial, the results showed that the weight gain rate, specific growth rate, survival rate and protein efficiency rate of hybrid grouper were significantly improved, and the feed conversion ratio of hybrid grouper in the 4% group (p < 0.05) was significantly reduced. The serum total protein, acid phosphatase, alkaline phosphatase and lysozyme of hybrid grouper in the 4% group were significantly higher than those in the control group, while the alanine transaminase, aspartate transaminase and malondialdehyde were significantly lower than those in the control group (p < 0.05). YC treatment significantly enhanced the trypsin, lipase and amylase activities (p < 0.05). Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes constituted the dominant phylum in grouper intestine. The relative abundance of Sphingomonas, Stenotrophomonas and Phyllobacterium in the YC groups was higher than that in the control group. The length and width of intestinal villi of grouper fed with YC diets were improved (p < 0.05). The protection against V. harveyi challenge in hybrid grouper was enhanced after YC treatment group, and the hybrid groupers fed with 4% YC diets experienced the highest cumulative survival rate of 67%. All these results suggested that the supplementation of 4% YC diets improved the growth performance, digestive enzyme activity, intestinal morphology, microbiota and disease resistance against V. harveyi of hybrid grouper.

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