Chemical requirements of feeding in rainbow trout, Oncorhynchus mykiss (Walbaum); palatability studies on amino acids, amides, amines, alcohols, aldehydes, saccharides, and other compounds

Abstract

Past studies on palatability perception and the chemical requirements of feeding in rainbow trout have focused on the amino acids. The stimulatory effectiveness of other classes of compounds remains largely unknown. In the present study representative members from several chemical classes were tested for their palatability to rainbow trout. Three heretofore untested amino acids (L‐norvaline, L‐norleucine and c‐aminocaproic acid), three amides (acetamide, valeramide and caproic amide), two alcohols (hexanol and octanol) and four sugars (o‐ribose, o‐glucose, D‐fructose and sucrose) were all mildly to highly palatable substances at their highest concentration tested. All other compounds tested within these classes did not evoke a positive behavioural response, demonstrating that rainbow trout are selective in thosecompounds deemed as palatable. Moreover, all of the aldehydes, trimethylamine, pyrrolidine and all of the amines except the alcoholic derivative, ethanolamine, were without effect. A provisional scheme for relating chemical structure versus the perception of palatability in rainbow trout is presented.