Effect of different dietary levels of potato protein concentrate supplemented with feed attractants on growth performance of rainbow trout (Oncorhynchus mykiss)

The potential of potato protein concentrate (PPC) as a replacement for fish meal (FM) protein was evaluated for rainbow trout (Oncorhynchus mykiss). Five diets were formulated by partial and total replacement of FM protein (20%, 40%, 60%, 80% and 100%, designated as PP20, PP40, PP60, PP80, PP100) with PPC (glycoalkaloid 23.2 mg kg−1 dry weight) and one experimental diet without PPC as control. Blood meal and a synthetic amino acid mixture and betaine were supplemented as feed attractants. Experimental diets were fed twice per day over a period of 56 days to triplicate experimental groups until apparent satiation. Within all groups the feed intake was unaffected compared to control (P>0.05). Feed conversion ratio was negatively affected when fish fed to PP60, PP80 and PP100. Above a FM protein replacement of 60% growth performance was reduced (P<0.05). The nutritional status (body composition, blood parameters) of all groups suggests no health impact of PPC at all. Compared to preceding studies, where the dietary incorporation of PPC was restricted to lower levels, the use of feed attractants (80 g kg−1 blood meal, 10 g kg−1 synthetic amino acids) increased inclusion levels of PPC up to 60% without any negative effects on fish performance. In conclusion, we presented an optimized PPC-based diet for rainbow trout as proxy for alternative aqua feeds and a sustainable development of aquaculture.