Alternative trout feeds match traditional diets on growth

CURRENT BRIEF VERSION: A new study in Animals reports that practical rainbow trout feeds built around insect meal, microalgae, microbial proteins, plant proteins, and aquaculture by-products performed about as well as a conventional diet on core production measures. In a 97-day trial, researchers tested four extruded diets — a conventional control plus three eco-efficient formulations — and found trout reached similar final weights, maintained a feed conversion ratio around 0.78, and had negligible mortality. Fillet composition and texture were also broadly comparable across diets, although fillet color shifted depending on the formulation, with some diets producing a more yellow hue and others paler flesh. (mispeces.com)

Why it matters: For veterinary and aquaculture professionals, the study adds to the evidence that reducing dependence on fishmeal and fish oil is becoming technically feasible in salmonid production, at least from a growth and basic flesh-quality standpoint. That said, the paper also underscores two practical constraints: sensory traits still matter, and sustainability claims depend heavily on ingredient sourcing and production systems. That caution lines up with other recent species work, including a 6-week Animals trial in juvenile yellowtail showing that replacing up to 35% of fishmeal protein with shark by-product-based composite protein mixtures maintained growth and survival, improved feed efficiency in some groups, but lowered EPA and DHA in some formulations. Together, the studies suggest formulation decisions still need to balance animal performance, product quality, fatty acid profile, and real-world economics. (mispeces.com)

What to watch: Expect follow-up work to focus less on whether fishmeal-free or low-marine-ingredient diets can support growth, and more on cost, lifecycle emissions, digestibility, fillet color, fatty acid retention, and market acceptance. (mispeces.com)