Evaluation of Commercial Diets for First-Feeding Spring Chinook Salmon

Abstract

In 2006, Bio-Oregon, Inc., the only commercial producer of cold-extruded moist diets (∼20–27% moisture) formulated for salmonids, announced that it would discontinue production of this diet line. One of these diets, BioDiet starter (19.5–21.5% moisture) was the primary feed used in many hatcheries that produce Chinook salmon Oncorhynchus tshawytscha. Thus, a feeding trial was conducted to identify an alternative starter diet for spring Chinook salmon. Five commercial diets were evaluated: Skretting BioVita (<10% moisture), EWOS Micro (<10% moisture), Rangen Starter (<10% moisture), Rangen Soft-Moist (14–17% moisture), and Silver Cup Soft-Moist (<13% moisture). Each dietary treatment was fed to quadruplicate groups of 200 randomly selected first-feeding fry reared in fiberglass tanks. Initial weight of the fish averaged 0.34 g/fish. The flow-through water supply was 12°C throughout the 8-week feeding trial. At the end of the study, fish fed Skretting BioVita exhibited significantly higher (P < 0.05) weight gain (3.4 g/fish) and feed efficiency (1.9 g gain/g feed) than fish fed the other diets. Fish fed Rangen Soft-Moist exhibited significantly lower (P < 0.05) weight gain (1.6 g/fish) and feed efficiency (1.2 g gain/g feed) than fish fed the other commercial diets. Survival rates were high (97–99%) and not significantly (P > 0.05) affected by dietary treatment. Carcass moisture and fat concentrations were significantly (P < 0.05) affected by the various diets. Carcass fat concentrations were significantly higher and carcass moisture concentrations were significantly lower in fish fed Skretting BioVita than in fish fed Rangen Starter, Rangen Soft-Moist, or Silver Cup Soft-Moist. Results of this study indicate that a moist starter diet is not required for rapid weight gain and high survival rates of first-feeding spring Chinook salmon.