Submitted to: Lipids
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/3/2013
Publication Date: 7/25/2013
Citation: Watson, A.M., Barrows, F., Place, A.R. 2013. Taurine supplementation of plant derived protein 1 and n-3 fatty acids are critical for optimal growth and development of cobia, rachycentron canadum. Lipids. 48:899-913. Interpretive Summary: The shortage of fish meal as an ingredient in fish feeds is well documented. Not making as many headlines is the shortage of fish oil that supplies not only energy but also the fatty acids that make eating fish good for heart and brain health. This study was conducted to determine if fish oil could be substituted by other sources of essential fatty acids. Although, these alternative sources of fatty acids are very expensive, cobia fed fish oil free diets grew well and were very healthy, demonstrating the fish require nutrients not ingredients. Additional research will be conducted to find cost effective substitutes.
Technical Abstract: We examined growth performance and lipid content in juvenile cobia, Rachycentron canadum, fed a taurine supplemented (1.5%), plant protein based diet with two fish oil replacements. The first fish oil replacement was a thraustochytrid meal (TM+SOY) plus soybean oil (~9% CL) and the second was a canola oil supplemented with the essential fatty acids (EFA) docosahexaenoic acid (DHA) and arachidonic acid (ARA) (~8% CL). The diet using the thraustochytrid meal plus soybean oil performed equivalently to the fish oil diet; both resulting in significantly higher growth rates, lower feed conversion ratios, and higher survival than the supplemented canola oil diet, even though all three diets were similar in overall energy and met known protein and lipid requirements for cobia. The poor performance of the canola oil diet was attributed to insufficient addition of EFA in the supplemented canola oil source. Increasing levels of EFA in the supplemented canola oil above 0.5g EFA kg-1 would likely improve results with cobia. When fish fed either of the fish oil replacement diets were switched to the fish oil control diet, fatty acid profiles of the fillets were observed to transition toward that of the fish oil diet and could be predicted based on a standard dilution model. Based on these findings, a formulated diet for cobia can be produced without fish products providing 100% survivorship, specific growth rates greater than 2.45 and feed conversion ratios less than 1.5, as long as taurine is added and EFA levels are above 0.5 g EFA kg-1.