Replacement of Fish Meal by Canola Meal in Rainbow Trout Diet for Evaluation of Growth and Ammonia Excretion

A 8-week feeding trial was conducted in order to investigated the effects of replacement of dietary fish meal by canola meal on growth performance, body composition and ammonia excretion rate (NH3) of the rainbow trout fingerlings. Experimental diets iso-protein (40%) and iso-caloric (3320 cal/g), were formulated with five levels of canola meal consisting of 0, 12, 24, 36 and 48 percent canola, which substituted 0, 25, 50, 75 and 100 percent of fish meal in the control diet, respectively. In each experimental treatment triplicate groups of rainbow trout fingerlings (15.2 ±2.3 g), were used in a completely randomized design. Fifty fish were assigned to each experimental diet treatment and held in 250 L tank. The results showed that replacement of fish meal by the canola meal up to 75 percent had no negative effects on growth performance. However, complete replacement showed a significance reduction (p> 0.05) in all growth parameters. Generally, body composition was affected by level of fish meal replacement, so that 100% replacement of fish meal by canola meal significantly affected dry matter and moisture content of body (p> 0.05). It was also revealed that replacement of fish meal by canola meal reduces ammonia excretion by fish, hence reducing environmental impact of aquaculture effluents. Economic efficiency of the diets was also affected by levels of replacement, achieving a highest value at 75% of replacement. In general, results showed that the canola meal has a good replacement potential, and can substitut fish meal in rainbow trout diet up to 75 percent.