Use of soy protein concentrate and novel ingredients in the total elimination of fish meal and fish oil in diets for juvenile cobia, Rachycentron canadum

Achieving true sustainability in fish farming requires the replacement of most of the fish meal and fish oil utilized as feedstuffs. The present experiment reports 2 feeding trials that resulted in the total replacement of fish meal and fish oil in juvenile cobia (Rachycentron canadum). The first trial was conceived as a 2 x 3 factorial design with three levels of fish meal replacement (FMR: 50, 75 and 100% of dietary protein) by soy protein concentrate (SPC), and two levels of mannan oligosaccharide (MOS) supplementation (0 or 0.3% of the diet). Since MOS has been reported to promote gut health and integrity, it was included in order to verify whether it would ease high levels of FMR. Lipids were supplied by menhaden oil. In the second feeding trial, fish meal was replaced by various combinations of SPC and soybean meal, again with or without MOS supplementation. In addition, some diets were supplemented with purified amino acids. Lipids were supplied by fish oil. A final diet (NOFM) was formulated using SPC, a marine worm meal, a nucleotide-rich yeast extract protein source, and MOS. In this last diet, lipids were supplied with a mix of soy oil and a DHA-rich algal meal, thereby completely eliminating both fish meal and fish oil. Over both feeding trials, juvenile cobia consistently exhibited excellent performance at 75% FMR and less. MOS did not have a significant effect, although a beneficial trend was observed in the first trial at 100% FMR. In the second trial, the fish fed the NOFM diet exhibited one of the best weight gains and feed efficiencies, with no mortality and no impact on muscle and liver composition. This result illustrates the crucial importance of the selection of feedstuffs for FMR and fish oil, since the NOFM diet did not receive amino acid supplementation. While this represents the first successful elimination of fish meal and fish oil in aquafeeds for cobia, the consistent, successful replacement of 94% of the fish meal in the other diets is actually more promising to the future as they solely utilized commodities traded (soy products) as replacement sources. which is the only road to true environmental and economical sustainability for the aquaculture industry. (C) 2009 Elsevier B.V. All rights reserved.