APPARENT DIGESTIBILITY COEFFICIENTS OF AQUA-PAK™ ELITE® 70, 65 AND 60, AND PROCISION® FOR RAINBOW TROUT, Oncorhynchus mykiss

In modern aquaculture, more and more effort is being applied to develop different types of ingredients to reduce reliance on ocean forage fish for feed protein. Aqua-Pak™ Elite® 70, 65 and 60 and ProCision® are commercially available protein concentrates designed to contain different levels of crude protein and essential amino acids for application in feeds for a variety of aquatic species (Table 1). To assess their nutritional value for rainbow trout, apparent digestibility of nutrients and energy (ADCs) and amino acid availability in compounded, extruded diets was determined. Fish with an average weight of 470 g were fed either a reference diet, or one of five different test diets created by blending the reference diet with each of the test ingredients (Menhaden fishmeal, special select (MFM), Aqua-Pak Elite 70, 65 and 60 and ProCision) in a 70:30 ratio (dry-weight basis). Diets were fed to fish in triplicate tanks for 15 days prior to collection of fecal samples. Data were analyzed by one way ANOVA and Dunnett's method to contrast test ingredients with MFM where P<0.05 was significant.

Dry matter and protein ADCs of Elite 70 were significantly higher than MFM while ProCision and Elite 60 were significantly lower than MFM (Table 2). Fat and energy ADCs of Elite 65, 60 and ProCision were significantly lower than MFM. Phosphorus ADCs of Elite 65 and ProCision were significantly higher than those of MFM. These results suggest that Aqua-Pak Elite 70 may have potential to replace fish meal in rainbow trout feeds. However, feeding trials are necessary to confirm this hypothesis.