A step towards sustainable aquaculture: Multiobjective feed formulation reduces environmental impacts at feed and farm levels for rainbow trout

International audience

English. Aquaculture is growing to meet the increasing demand for aquaculture products but is not free of environmental impacts. One solution is to improve how feed are formulated, limiting the environmental impact of fish production. Multiobjective (MO) formulation, which aims for a compromise between lower cost and lower environmental impacts, appears to be a promising solution to reduce the environmental footprint of aquaculture production. The objectives of this study were to design an eco-friendly trout feed (ECO-diet) using MO formulation and to compare its zootechnical and environmental performances to those of a commercial feed (C-diet) containing 16% fishmeal and 6.5% fish oil. MO formulation changed the composition of the diet greatly, which decreased environmental impacts of the feed as well as its price. It increased the number of ingredients used but reduced the use of fishmeal and fish oil by half. MO formulation also led to the elimination of soy products, faba bean, and gluten in favour of processed animal co-products that have high protein contents and low climate change impact. Rapeseed oil also disappeared from the ECO-diet due to its major contribution to land use, eutrophication, and acidification and, to a lesser extent, climate change. Overall, the ECO-diet had high digestibility, which differed little from that of the C-diet. Mean fish body weight after 12 weeks of growth did not differ significantly from that obtained with the C-diet, but analysis of fish growth curves indicated that the ECOdiet could lead to lower growth in the long term. This observation was consistent with the significantly lower feed intake in fish fed the ECO-diet. The decrease in impacts observed at the feed level was also observed at the farm level, although less so for eutrophication, non-renewable energy use, and climate change calculated per kg of body weight gain. MO formulation is a useful tool to reduce the environmental footprint of aquaculture production without compromising animal performances or necessarily increasing production cost.