Effects of Dietary Cottonseed and/or Canola Oil Inclusion on the Growth Performance, FA Composition and Organ Histology of the Juvenile Rainbow Trout, Oncorhynchus mykiss

Abstract

This study aimed at demonstrating the effects of total and 50% dietary fish oil replacement by cotton seed and canola oils and a mixture of these vegetable oils (VOs) on growth, tissue fatty acid composition and histology of digestive organs in the juvenile rainbow trout for 84 days. Five iso-nitrogenous and lipidic diets were formulated to replace dietary fish oil (FO) totally by cotton seed oil (CSO), canola oil (CO) and an equal or 50% FO/ 50% VO mixture. Duplicate groups of 50 fish (similar to 15 g) were fed two times daily to apparent satiation. Growth performance, feed efficiency and viscerosomatic index were not influenced by dietary treatments (P>0.05). However, hepatosomatic index was significantly higher (P<0.05) in fish fed with CSO and CSO50/CO50 diets. Fish fed CSO or CO diets had significantly lower levels of n-3 highly unsaturated FAs and increased levels of 18:2n-6 in the whole body FA composition (P<0.05). Furthermore, liver had significantly higher levels of docosahexaenoic acid and arachidonic acid than those in the fish whole body. Results suggest that the 50% replacement of dietary fish oil by cotton seed oil and canola oils in equal amounts could be possible without compromising growth and overall well-being in the juvenile rainbow trout.