Evaluation of Tower and Candle rapeseed (canola) meal and Bronowski rapeseed protein concentrate as protein supplements in practical dry diets for juvenile chinook salmon ( Oncorhynchus tshawytscha)

Abstract

A laboratory study and a pilot-scale hatchery experiment were carried out to determine the acceptability of rapeseed products as protein supplements in diets for chinook salmon. Replacement of 10 and 13% of the protein in a modified Abernathy dry diet with protein from Tower or Candle rapeseed meal or Bronowski rapeseed protein concentrate did not alter growth rate, food or protein utilization, body composition, thyroid or pituitary cytology, osmoregulatory capacity, health or mortality of chinook salmon. However, growth rate and food (protein) utilization were reduced when 25% of protein was replaced by rapeseed meal, but not when replaced by Bronowski rapeseed protein concentrate. Condition factors of chinook fed rapeseed products at the intermediate or highest levels were often significantly elevated. Hatchery performance of chinook salmon fed a dry diet where 13% of protein was provided from Tower meal was similar to that when Oregon moist pellets were fed except for a compensatory increase in thyroid activity in the former fish. It is concluded that rapeseed products of the canola type are good protein supplements for chinook salmon and can comprise 13 to 16% of dietary protein (16 to 20% of dietary dry matter).