Alternative trout feeds match conventional performance in new study

CURRENT BRIEF VERSION: A new study in Animals reports that practical rainbow trout feeds built with insect meal, microalgae, single-cell ingredients, selected plant proteins, and aquaculture by-products matched conventional feed on key production measures, including growth, body composition, nutrient retention, and flesh quality. The work, by Filippo Faccenda, Elia Ciani, and Lorenzo Rossi, tested four extruded diets: a conventional control and three eco-efficient alternatives, including formulations with and without processed animal proteins. The broader finding fits with a growing body of aquaculture nutrition research showing that insect-, algae-, and by-product-based ingredients can replace part of the fishmeal and fish oil burden without obvious losses in performance, if formulations are balanced carefully. That pattern is not limited to trout: a recent Animals study in juvenile yellowtail found that replacing up to 35% of fishmeal protein with shark by-product-based composite mixtures did not reduce growth, feeding rate, or survival over six weeks, and some formulations improved feed efficiency, although EPA and DHA levels were lower in some diets. (mdpi.com)

Why it matters: For veterinary professionals working in aquaculture, the study adds practical evidence that lower-dependency feed strategies can move beyond proof-of-concept and into commercially relevant formulations. That matters because salmonids remain major users of marine ingredients in aquafeed, and pressure to diversify protein and omega-3 sources is rising as aquaculture expands. At the same time, the sustainability case isn’t automatic: life-cycle work in trout systems suggests insect meal can introduce energy and greenhouse gas trade-offs depending on how the ingredient is produced, and by-product substitutions can also shift fatty acid profiles, so performance data still need to be weighed alongside sourcing, digestibility, fish welfare, fillet composition, and environmental footprint. (iffo.com)

What to watch: The next question is whether these formulations hold up at commercial scale on cost, ingredient availability, regulatory fit, product quality, and full life-cycle performance, not just growth in controlled trials. (eur-lex.europa.eu)