Determination of the Effects of Fish vs Plant vs Meat Protein-based Diets on the Growth and Health of Rainbow Trout

Abstract

Rahnema, S., Borton, R. and Shaw, E. 2005. Determination of the effects of fish vs plant vs meat protein-based diets on the growth and health of rainbow trout. J. Appl. Anim. Res., 27: 77–80. One hundred eight fingerling rainbow trout were used in an experiment to compare feed consumption, growth rate, gain-to-feed efficiency and live and carcass characteristics for rainbow trout receiving diets containing fish meal (FM), plant protein (PP), or feather meal and meat meal (FMMM), based diets. Six trout were housed in an 18″ × 18″ × 22″ cage (18 total cages) and nine of these cages (three per treatment) were placed in each of two 1000-gallon tanks. Fish were fed twice per day all the feed that they would eat within 30 min. Feed consumption and fish weights (by cage) were measured once every other week. At the end of the feeding trial, one fish from each cage was harvested, frozen in water and stored at −25C. The left half of each trout was excised, wrapped in aluminium foil and baked in an oven at 163C for 30 min. The trout were then divided into approximately 1.0 cm 3 cubes (about 20 g) and presented to the panel for evaluation of flavour, off flavour, tenderness, juiciness and overall acceptability of the meat. The right half of each trout was excised and used for laboratory analyses of moisture, fat, ash and protein content. The Ca content of the PP was lower than FM and FMMM diets. Fish consuming the PP diet had consumed less feed (P<0.00) and had a lower average daily gain (P<0.02) than the fish on FM or FMMM diets. Feed-to-gain ratios for PP and FM diets were similar and both were lower (P<0.00) than that of the FMMM diet. There were no differences due to treatment for moisture, fat, crude protein or ash content of the trout. Trout fed the FM diet were juicier and tenderer than the trout fed the PP diet. It is concluded that a meat scrap ration may substitute for the commercial fish meal ration if it is economically available.