Replacing fishmeal with plant protein in Atlantic salmon (Salmo salar) diets by supplementation with fish protein hydrolysate

TLDR

The study examined how an 80 % plant protein diet, with or without fish protein hydrolysate, affects growth and gut health in Atlantic salmon. Salmon were fed one of four diets: a 35 % fishmeal control, an 80 % plant protein diet with 15 % fishmeal, an 80 % plant protein diet with 5 % fishmeal plus 10 % partly hydrolysed protein, or an 80 % plant protein diet with 5 % fishmeal plus 10 % soluble protein hydrolysate. Fish on the 80 % plant‑protein/15 % fishmeal diet grew significantly smaller, but inclusion of partly‑hydrolysed protein restored growth to control levels, increased blood amino acids (48 % and 27 % more branched‑chain amino acids for diets C and D), and altered gut microbiota by reducing α‑diversity and the abundance of Spirochaetes, Moritellaceae, Psychromonadaceae, Helicobacteraceae, and Bacteroidaceae.

Abstract

The effects of feeding an 80% plant protein diet, with and without fish protein hydrolysate (FPH) supplementation, on the growth and gut health of Atlantic salmon were investigated. Fish were fed either (A) a control diet containing 35% fishmeal, (B) an 80% plant protein diet with 15% fishmeal, (C) an 80% plant protein diet with 5% fishmeal and 10% partly hydrolysed protein, or (D) an 80% plant protein diet with 5% fishmeal and 10% soluble protein hydrolysate. Fish on the 80% plant- 15% fishmeal diet were significantly smaller than fish in the other dietary groups. However, partly-hydrolysed protein supplementation allowed fish to grow as well as fish fed the control 35% fishmeal diet. Fish fed the FPH diets (diets C and D) had significantly higher levels of amino acids in their blood, including 48% and 27% more branched chain amino acids compared to fish on the 35% fishmeal diet, respectively. Plant protein significantly altered gut microbial composition, significantly decreasing α-diversity. Spirochaetes and the families Moritellaceae, Psychromonadaceae, Helicobacteraceae and Bacteroidaceae were all found at significantly lower abundances in the groups fed 80% plant protein diets compared to the control fishmeal diet.