Study finds insect- and algae-based trout feeds match standard diets

CURRENT BRIEF VERSION: A new Animals study reports that practical rainbow trout feeds made with insect meal, microalgae-derived omega-3s, selected plant proteins, single-cell ingredients, and aquaculture by-products delivered growth, body composition, nutrient retention, and fillet quality broadly comparable to a conventional control diet. The researchers tested four extruded diets — a standard control plus three eco-efficient formulations labeled No-PAP, PAP, and Mix — and found that the alternative formulations maintained key production and quality benchmarks in Oncorhynchus mykiss. The work adds to a growing body of evidence that trout diets can rely less on traditional fish meal and fish oil without obvious performance tradeoffs in well-formulated rations. Related work in juvenile yellowtail has pointed in the same direction: an Animals feeding trial found that replacing up to 35% of fish meal protein with shark by-product-based composite mixtures did not significantly affect growth or survival, although some formulations lowered EPA and DHA levels, underscoring the need to watch fatty acid profiles as marine ingredients are reduced. (mdpi.com)

Why it matters: For veterinary professionals working in aquaculture, the study is another signal that feed sustainability and fish performance don’t have to be at odds. As aquaculture output continues to grow globally, pressure is increasing to reduce dependence on marine ingredients tied to wild fisheries. Insect proteins are already permitted in aquafeed in the EU under established rules, and microalgae are attracting attention as a source of DHA and EPA, but questions remain around ingredient consistency, palatability, economics, and downstream effects on fish health, welfare, and fillet quality in commercial settings. Findings from yellowtail also suggest that by-product proteins can help cut fish meal use without hurting growth, while still leaving open questions about nutrient composition and product quality when key omega-3s fall. (fao.org)

What to watch: The next step is whether these formulations hold up in longer commercial trials, cost out competitively, and show consistent health and quality outcomes across farms and production stages. It will also be worth watching whether alternative protein blends preserve desirable fatty acid profiles as fish meal and fish oil inclusion falls. (news.ucsc.edu)