Novel ingredients and underexploited feed resources to improve sustainability of farmed fish species.

abstractita

Seeking for new or underexploited feed protein sources to replace or complement conventional ones in farmed fish diet, is considered a suitable way to afford the sustainability issue generated by a growing aquaculture industry in the next future and to reduce or mitigate possible adverse effects of certain high vegetable diets on growth and health of cultured carnivorous fish species. The sustainability issue also drove the interest towards protein-rich raw or processed feed materials that comply with the principles of the circular economy and/or come from lower trophic levels. In this directions, the present PhD thesis, carried out within the project AGER2- SUSHIN proposes a substantial step beyond the current state of knowledge on the nutritive value of novel or underexploited protein-rich ingredients in carnivorous fish species. It includes three contributions. The first two, consist in studies aimed at estimating the nutritive value (nutrient composition, in vivo and in vitro digestibility) of a range of novel or conventional protein-rich ingredients which digestibility have been poorly investigated to date, to explore their suitability as protein sources in diets for Rainbow trout and European sea bass. The selected panel of ingredients includes, poultry by product meals with a different proportion between chicken and turkey leftovers, commercial Hermetia illucens pupae meals, and a panel of whole-cell microalgae and cyanobacteria dried biomasses. The third contribution deals with an experiment aimed at studying growth performance, liver and gut histology, gut BBM enzyme activity, inflammatory markers and innate immune parameters of Rainbow trout (Onchorhynchus mykiss) fed diets deprived of fish meal, where graded levels of vegetable proteins were replaced by H. illucens pupae meal (HM) or/and poultry by-product meal (PBM). The results obtained so far, provide nutritional support basis to a reliable use of novel protein sources in fish feeds like HM and certain whole-cell microalgae and cyanobacterial dried biomasses or underexploited protein sources (PBM) in developing a new generation of sustainable and healthy fish diets that minimize the use of conventional proteins and meet the circular economy principles.