An assessment of processing effects on the nutritive value of marine protein sources for juvenile chinook salmon ( Oncorhynchus tshawytscha)

Abstract

This study was undertaken to assess the nutritional value of marine fish protein sources processed in different ways for juvenile chinook salmon reared in fresh water. The protein sources compared were a freeze-dried pollock muscle and euphausid mix (9:1) (FPE), and three whole herring meals processed differently from a common lot of raw herring. A casein-gelatin mix supplemented with arginine and DL-methionine (CS) served as a reference protein source. The five protein sources were each tested at three protein concentrations in isocaloric diets. FPE was also assessed at two additional protein levels. Protein was replaced by dextrin and glucose on an estimated metabolizable energy basis. Each diet was fed to duplicate groups of fish held at 10.5°C on a natural photoperiod for 42 days. All fish were fed daily to satiation. Two groups received Oregon moist pellets (OMP-2), a practical hatchery diet. Each of the various methods employed to evaluated protein quality yielded different relative values in comparison to FPE, which was judged to be the best protein source on the basis of growth rate response and assays based on body protein gain. Low temperature (75°C) dried herring meal had slightly reduced protein quality compared to freeze-dried herring meal, whereas the high temperature (150°) dried meal had dramatically reduced protein quality. High estimates of protein quality were obtained for CS. However, this protein source was not as palatable as the low temperature dried marine protein sources and consequently growth was reduced.