Intestinal microbiota was closely related to feed efficiency of Larimichthys crocea fed two fishmeal-free diets

This study examined the link between feed efficiency (FE) and intestinal microbiota in Larimichthys crocea fed on fishmeal-free diets. Two types of fishmeal-free diets were formulated: a plant protein-based feed (Group P) and a mixed-protein feed (Group M). These two types of diets were utilized to rear the two groups of L. crocea for 28 days, each consisting of individuals that were 18 months old. Initial and final weights, as well as feed consumption, of the experimental fish were documented. FE was calculated for each fish based on this data. Post-experiment, samples were taken from fish with high and low FE for 16S rRNA gene sequencing. In the Group M, the high and low FE fishes were designated as MH (proximal intestine, MHp; distal intestine, MHd) and ML (proximal intestine, MLp; distal intestine, MLd). In the Group P, the high and low FE fishes were designated as PH (proximal intestine, PHp; distal intestine, PHd) and PL (proximal intestine, PLp; distal intestine, PLd). The results indicated that in Group M, there was no significant difference in microbial community structure between MH and ML, but the microbial diversity and species richness in MH were higher than that in the corresponding ML. MHp showed a significantly higher abundance of the orders Elsterales, Frankiales, and the family Hyphomicrobiaceae compared to MLp. MHd, in comparison to the MLd, had a significant higher abundance of the order Burkholderiales. There was also no significant difference in microbial community structure between PH and PL, but the microbial diversity in PH was lower than that in the corresponding PL. PHp showed a significantly higher abundance of Proteobacteria and GammaProteobacteria compared to PLp; whereas, the significant difference between PHd and PLd was only present in PLd. Microbial functional prediction analysis showed that the intestinal microbiota was mainly involved in carbohydrate metabolism, energy metabolism and vitamin metabolism pathways. These findings of this study contribute to our further understanding of the relationship between intestinal microbiota and the FE traits of the host. The microbial markers found between the high and low FE groups can offer insights and serve as a reference for subsequent research aiming to improve FE using Nutrition and Genetic Selection Techniques.