Environmental impact of the inclusion of alternative raw materials in diets for gilthead seabream

The study used Life Cycle Assessment (LCA) to analyse the effect on global warming potential (GWP) of the partial and total replacement of fishmeal with blends of alternative protein meals in diets for gilthead seabream. A total of 360 seabream (64 ± 1.3 g) were fed five diets (three tanks per diet): a control diet (FM100 with 590 g/kg fishmeal) or four alternative diets where fishmeal was replaced at 75% (FM25), 90% (FM10), and 100% (FM0) by protein blends consisting of Iberian pig meal (IPM, 237-328 g/kg) and vegetable protein meals (soybean, pea and sunflower meals) (373-478 g/kg). An additional fishmeal-free diet also contained 50 g/kg of microalgae Isochrysis aff. galbana (T-Iso) (FM0+). Final weight was higher (+48%; P<0.05) and feed conversion ratio lower (−29%; P<0.05) in fish fed FM100 and FM25 diets compared with FM0 diet, with intermediate values for FM10 and FM0+ diets. The LCA included the impact of aquafeed production, referred to 1 kg increase of fish. The GWP increased with fishmeal replacement, from 1.15 kg CO2-eq in FM100 to 2.45 kg CO2-eq in FM0 diets. In FM100 diet, fishmeal contributed to 47% of the total impact, followed by wheat meal (20%), and soybean oil (20%). In alternative diets, IPM was the major contributor to GWP (50% to 60%), followed by soybean meal (6% to 8). In FM0+ diet, T-Iso contributed to 14% of total GWP. Based on our preliminary results, the replacement of fishmeal at 75% with a blend of Iberian pig meal and vegetable proteins seems to represent the best trade-off, both in terms of growth and environmental performance.