GROWTH, BLOOD METABOLIC PARAMETERS AND GUT HEALTH STATUS IN RAINBOW TROUT (Oncorhynchus mykiss) FED FISH MEAL-FREE DIETS SUPPLEMENTED WITH CONVENTIONAL FEED ADDITIVES OR DRIED MICROBIAL BIOMASS AND RED SWAMP CRAYFISH MEAL AS FEED SUPPLEMENT

The readily available and cost-effective plant protein-rich ingredients have become the main protein sources used in aquafeeds to substitute unsustainable marine-derived ones. However, the transition to plant-based diets is more difficult to achieve for carnivorous fish, like salmonids, in which certain plant protein-rich ingredients can cause adverse effects on growth, liver integrity and gut health. In this regard, functional feeds represent an interesting solution to mitigate these drawbacks, even at low dietary inclusion. The present study was aimed at exploring the nutraceutical effects of low dietary inclusions of conventional feed additives (nucleotides and sodium butyrate) or innovative potential feed supplements such as Louisiana red swamp crayfish meal (RCM) and dried microbial biomass from intact cells of Tetraselmis suecica (TS) and Artrhospira platensis (spirulina; AP) in fish meal-free diets during a 104 day feeding trial performed on rainbow trout (Oncorhynchus mykiss).