|Rawles, Steven - Steve|
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2012
Publication Date: 3/25/2013
Publication URL: DOI: 10.1080/15222055.2012.713896
Citation: Faukner, J., Rawles, S.D., Proctor, A., Sink, T.D., Chen, R., Philips, H., Lochmann, R.T. 2013. The effects of diets containing standard soybean oil, soybean oil enhanced with conjugated linoleic acids, menhaden fish oil, or an algal docosahexaenoic acid supplement on channel catfish performance, body composition, sensory evaluation, and storage characteristics. North American Journal of Aquaculture. 75:252–265. Interpretive Summary: One of the health benefits of consuming fish is the amount of Omega-3 fatty acids, which are higher in seafood than in red meat. In particular, levels of the omega-3 fatty acid DHA—short for docosahexaenoic acid—are especially high in fish. The fatty acid profile of farmed fish can be manipulated for human health benefits by including different types of oils in fish feeds. Much of the DHA in farmed fish, for example, comes from the fish oil included in the diet. However, world supplies of fish oil are at the breaking point due to overharvesting of the world’s oceans. And stiff competition among buyers means that prices for fish oil have become extremely high. The aquaculture industry is trying to move away from using fish oil by increasing the proportion of vegetable oils in fish feeds. However, consumers and human nutritionists are concerned that beneficial fatty acids in fish may be diluted this way. Another fatty acid with benefits to human health, including reduced risk of cancer and better weight management, is known as Conjugated Linoleic Acid, or CLA. We conducted a 25-week experiment to determine how four different oils in the diet of channel catfish affected fish growth, concentration of beneficial fatty acids in the fillets, fillet quality after cold storage, and consumer taste preferences. The four oils used in the diets were fish oil, soybean oil, soybean oil containing CLA, and oil extracted from algae with high concentrations of DHA. The four oils did not reduce growth or change the quality of the fillets after refrigeration and freezing. Only fish fed the diet containing CLA in the oil ended up with CLA in the fillets, but the levels of omega-3 DHA were slightly reduced. Although fish fed diets containing fish oil or DHA had higher amounts of DHA, the fillets were less favored by consumers than fillets from fish fed soybean oil or soybean oil with CLA. Generally, fish fed a diet containing CLA in the oil ended up with amounts of CLA in the fillet considered good for human health. And the fillets of these fish were among the highest in consumer preference.
Technical Abstract: Fish consumption is a common method of obtaining beneficial n-3 highly unsaturated fatty acids (HUFAs), but increased use of vegetable oils in fish diets to reduce dependence on fish oil dilutes these HUFAs. Conjugated linoleic acids (CLA) are also considered beneficial for human health. Therefore, we investigated four different lipid sources in channel catfish Ictalurus punctatus diets to enhance fatty acid profiles of fillets to benefit human health while maintaining or improving fish performance. In a 175-d growout trial, channel catfish (mean +/- SE 71.4 +/- 0.1 g) were fed a commercial 32%-protein diet supplemented with 2% lipid from: soybean oil (SBO), soybean oil enhanced with conjugated linoleic acids (CLA), menhaden fish oil (MFO), or an algal extract of Schizocyhtrium sp. high in 22:6n-3 (DHA). Diet effects were assessed by measuring fish growth performance, muscle proximate and fatty acid composition, sensory characteristics of fillets, consumer taste preferences, and oxidative stability of fillets during cold storage. There were no differences in fish growth performance or proximate composition. Only fish fed the CLA diet contained CLA in the muscle. Fish fed the MFO or algal DHA diets had higher concentrations of 22:6n-3 in the muscle compared to fish fed SBO or CLA diets. Sensory evaluation and consumer preference testing were more favorable for fillets from fish fed SBO or CLA diets than from fish fed MFO or algal DHA diets. There were no differences in storage characteristics of fish refrigerated at 4C for two weeks or frozen at -18C for four weeks. Fillets from fish fed the MFO diet yielded the highest concentration of fatty acids for human health benefits, followed by the fillets from fish fed the algal DHA diets. The CLA diet produced increased fillet concentrations of CLA that are also beneficial for human health.