Effect of algal incorporation on growth, survival and carcass composition of rainbow trout (Oncorhynchus mykiss) fry

A nutritional assay has been conducted with rainbow trout fry (Oncorhynchus mykiss) using a biomass of photosynthetic micro-organisms. The algal biomass was incorporated in the feed at increasing levels (12.5%, 25% and 50%) in order to verify the effects on survival (%), growth (length and mass) and carcass quality of the fish (skin color, water, protein and lipid content). Two commercial feeds (CF, as sold, and 0% A, reprocessed without algae) have been used as controls. After eight weeks at 10 °C, the growth has been significantly reduced in fish fed the feeds containing 25% and 50% algae diets (P < 0.01). Moreover, an incorporation of algae higher than 12.5% in the feed led to a increase of water content (CF versus other diets; P < 0.01) and TL (CF versus 50% A; P < 0.01) (wet basis) content of carcasses. Survival was 100% in all treatment groups. Under the experimental conditions used, the results obtained show that a maximum of 12.5% of algal biomass can be incorporated in the feed for rainbow trout fry (O. mykiss) without negative consequences on growth and body content in lipids and energy of fish.