Evaluation of feed attractants in potato protein concentrate based diets for rainbow trout (Oncorhynchus mykiss)

A feeding trial was carried out with rainbow trout to evaluate different feed attractants in isonitrogenous (472 ± 8 g CP kg−1) and isoenergetic (21.7 ± 0.3 MJ kg−1) diets upon fish meal (FM) replacement by potato protein concentrates (PPCs) at 50% and low glycoalkaloid content (7 mg kg−1). After one week of acclimatization, two fish meal diets — one with 7 mg kg−1 synthetic glycoalkaloids (GFM) and one control (FM), a PPC control without additional attractants (PP), and six PPC diets with blood meal (BM 4 or 8%), mussel meal (MM 4 or 8%) and a free amino acid mixture (AM 0.5 or 1.0% alanine, glycine and betaine) as attractant were fed in triplicate until apparent satiation over a period of 56 d to the experimental groups (7 fish per tank, average initial weight 52.8 ± 0.3 g).All PPC groups revealed reduced growth when compared to the fish meal group (FM). Furthermore, all PPC groups exhibited lower growth when compared to the GFM group fed at comparable glycoalkaloid concentrations suggesting antinutritional effects apart from glycoalkaloids. Nevertheless, a PER of more than 2 in all groups indicated acceptable protein utilization in PPC groups, additionally supported by FCR ranging between 0.92 and 1.15. Highest daily feed intake (DFI) was observed in the FM and GFM group, but reduced in all PPC groups. Among the attractants used, BM and AM resulted in the highest DFI. A good nutritional status did not reveal severe impact of PPC in general.

► This study evaluated feed attractants in PPC based diets for rainbow trout.
► Blood meal, mussel meal and free AA were used as attractants in varying amounts.
► All PPC diets revealed reduced growth compared to fish meal control.
► Blood meal and free AA resulted in the highest DFI among the attractant groups.
► Good nutritional status revealed no negative impact of PPC in general.