  To support the expected increase in aquaculture production during the next
years, a wider range of alternative ingredients to fishmeal is needed, towards
contributing to an increase in production sustainability. This study aimed to
test diets formulated with non-conventional feed ingredients on gilthead
seabream (Sparus aurata) growth performance, feed utilization, apparent
digestibility of nutrients and nutrient outputs to the environment. Four
isonitrogenous and isoenergetic diets were formulated: a control diet (CTRL)
similar to a commercial feed and three experimental diets containing, as main
protein sources, plant by-products, glutens and concentrates (PLANT); processed
animal proteins (PAP); or micro/macroalgae, insect meals and yeast (EMERG).
Diets were tested in triplicate during 80 days. The (EMERG) treatment resulted
in lower fish growth performance, higher FCR and lower nutrient and energy
retentions than the other treatments. The lowest protein digestibility was
found for the EMERG diet, which caused increased nitrogen losses. The PLANT and
PAP treatments resulted in better fish growth performance, higher nutrient and
energy retentions, and lower FCR than the CTRL treatment. The significant
improvement in FCR found for fish fed PLANT and PAP diets and the high protein
digestibility of these diets contribute towards minimizing the environmental
impacts of seabream production
