- (1) Aarhus University, grid.7048.b, AU
- (2) Technical University of Denmark, grid.5170.3, DTU
- (3) BioMar (Denmark), grid.424148.f
The current study investigated the effects of fishmeal quality (low (LB) and high (HB) levels of endogenous biogenic amines) and feed extrusion temperatures (100 and 130 °C) on protein oxidation indicators and amino acids racemization (AAR) in extruded fish feed. Furthermore, the study investigated the accompanying effects on feeding the diets to juvenile rainbow trout (Oncorhynchus mykiss) on fish growth performance, in vivo amino acids (AAs) digestibility, and liver and plasma metabolites following an 8-week feeding trial. A principal component analysis (PCA) showed that better growth performance, secondary oxidation products, and racemized methionine correlated positively with a low content of biogenic amines, whereas the primary oxidation product, protein hydroperoxides, and in vivo AAs digestibility correlated positively with high content of biogenic amines. At an extrusion temperature of 100 °C, the growth performance of the fish decreased when the content of biogenic amines increased. In contrast, at an extrusion temperature of 130 °C, the growth performance was unaffected by the level of biogenic amines. The latter could be a consequence of the higher level of protein oxidation of LB fishmeal compared to HB fishmeal at this temperature. Higher levels of liver pyruvate and plasma lactate together with high level of betaine and AAs in both liver and plasma were associated with the LB fishmeal diets. The lower concentration of AAs especially in liver of fish fed with HB fishmeal demonstrated that these AAs might not be supplied sufficiently for the tricarboxylic acid cycle to generate energy and therefore a decreased growth was found in fish fed this diet. Furthermore, the results indicated that biogenic amines and feed attractants such as betaine are more decisive for evaluating the quality of fishmeal than protein quality parameters.