Krill hydrolysate free amino acids responsible for feed intake stimulation in Atlantic salmon ( Salmo salar).

The appetite-stimulating effect of krill hydrolysate ( KH), free amino acids and specific water-soluble low molecular N-compounds was explored in a short feeding trial with Atlantic salmon. A 100 g kg−1 fish meal positive ( MFM), a 30 g kg−1 fish meal negative control ( LFM) and six more LFM diets were produced added known attractants for fish- KH at two levels: low ( LAK) or high ( HAK), AMP, choline chloride ( CC); an amino acid mix resembling the free amino acid composition of KH ( AA) or a mix of AMP, CC and AA ( ACA). HAK, ACA and AA showed highest feed intake and significantly higher plasma phospholipids and cholesterol. The lower performing treatments ( LFM, AMP) showed higher liver lipids and hepatosomatic index. CC induced reduced liver lipids and increased plasma phospholipids and cholesterol. Appetite regulating neuropeptide gene expression analysis (q PCR) was performed in fish fed LFM, HAK and AA. Pyy showed the highest postprandial expression in LFM, whereas the expression of the anorexigenic neuropeptides cart, pomca1, pomca2 and pomca2s was low. These apparently contradictory results may be explained by initial appetite stimulation by HAK and AA, resulting in higher feed intake, followed by satiation and appetite downregulation. [ABSTRACT FROM AUTHOR]