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 juvenile channel catfish performance, hematology

Authors: FAUKNER, JIMMY - University Of Arkansas At Pine Bluff; Rawles, Steven - Steve; SINK, TODD - Texas A&M University; CHEN, RUGUANG - University Of Arkansas At Pine Bluff; PHILIPS, HAROLD - University Of Arkansas At Pine Bluff; PROCTOR, ANDREW - University Of Arkansas; LOCHMANN, REBECCA - University Of Arkansas At Pine Bluff

Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/6/2014
Publication Date: 4/1/2015
Publication URL: http://dx.doi.org/10.1080/15222055.2014.999848
Citation: Faukner, J., Rawles, S.D., Sink, T.D., Chen, R., Philips, H., Proctor, A., Lochmann, R. 2015. 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 juvenile channel catfish performance, hematology. North American Journal of Aquaculture. 77(2):217-229.

Interpretive Summary: In order to reduce feed costs and to address concerns that aquaculture world-wide uses most of the fish oil harvested from the ocean, commercial diets for channel catfish contain little or no marine fish oil. However, fish oils are high in omega three, unsaturated fatty acids that are linked to a multitude of human health benefits. So replacing fish oil in fish feed with vegetable oils lowers the concentrations of healthy fats in farmed fish fillets, and reduces the potential health benefits of eating farm-raised fish. There are new vegetable oils emerging in the feed ingredient market, however, that have been enhanced with healthy unsaturated fats. Many of these oils have not been tested in catfish. We compared two different enhanced vegetable-based oils with marine fish oil (menhaden) and a regular vegetable oil (soybean) in diets for fingerling channel catfish, i.e., small catfish grown for stocking grow-out ponds. One of the two enhanced oils was extracted from algae commercially grown to contain high levels of the healthy and highly unsaturated, omega three fatty acid DHA, or docosahexaenoic acid. The second modified oil was a soybean oil enhanced with conjugated linoleic acid (CLA)—another healthy fatty acid. CLA has been linked to reduced risk for cancer and better weight management in humans. Catfish fingerlings were fed diets containing each of the four oils and grown from 4 inches to 8 inches in two months. The diet containing fish oil produced fish with slightly less pounds of feed per pound of fish grown, but there were no differences in overall average fish weight, protein and fat content of the fish, or indicators of fish health and resistance to disease among fish fed the four oils. Three of the test oils—fish oil, algae oil, and soybean oil enhanced with CLA—increased the amount of healthy fatty acids measured in the fish more so than fish fed the diet with regular soybean oil. And the algae oil was about as effective as fish oil in increasing the amount of healthy DHA in the fish. This study shows producers that enhanced vegetable oils can replace fish oil in catfish fingerling feed without compromising fish yield or fish health, while simultaneously improving the nutritional profile of the fingerlings destined for grow-out for consumers. Moreover, these results will be used to further test whether the enhanced vegetable oils can be fed to catfish grown to market size with similar or better retention of desirable fatty acids and high consumer acceptance of the fillets.

Technical Abstract: Current commercial diets for Channel Catfish contain little or no marine fish oil to reduce diet cost and address environmental concerns. However, there is conflicting data on the effects of fish oil and other lipid sources in juvenile Channel Catfish, and some novel lipids have not been tested against traditional ones. We investigated the effects of four different lipid sources for potential use in juvenile Channel Catfish Ictalurus punctatus diets by measuring fish growth performance, proximate and fatty acid composition of muscle, nonspecific immune response, and hematological parameters. In a 63-d feeding trial, Channel Catfish (mean +/- SE, 11.2 +/- 0.0 g) were fed a commercial 32% protein diet supplemented with 2% lipid from standard soybean oil (SBO; control), soybean oil enriched with conjugated linoleic acids (CLA), algal (Schizochytrium sp.) docosahexaenoic acid extract (DHA), or menhaden fish oil (MFO). Fish fed the MFO diet had improved feed conversion compared to fish fed the SBO, CLA, or DHA diets. There were no other differences in fish growth performance or proximate composition, and no differences among treatments in nonspecific immune responses or hematological parameters. As expected, fatty acid composition of muscle reflected that of the diets, with fish fed the MFO, DHA or CLA diets containing higher levels of healthful fatty acids (DHA or CLA) than the SBO control. Future trials will address methods to increase target levels of these fatty acids using diets with little or no fish oil, and to optimize retention of desirable fatty acids in market-size fish.