Growth Performance and Proximate and Fatty Acid Compositions of Channel Catfish, Ictalurus punctatus, Fed for Different Duration with a Commercial Diet Supplemented with Various Levels of Menhaden Fish Oil

A 15-wk study was conducted to evaluate the effect of supplemental menhaden fish oil levels and feeding duration on growth performance and tissue proximate and fatty acid (FA) compositions of juvenile channel catfish, Ictalurus punctatus. Dietary fish oil levels had no effect on final weight gain, feed efficiency, and survival of channel catfish. Tissue lipid contents were directly correlated to dietary lipid levels, while moisture contents were inversely related to dietary lipid levels. Fillet moisture contents progressively decreased, whereas fillet lipid increased with increasing feeding duration. Significant increase in saturated and total n-3 FAs and decrease in monoenoic and total n-6 FA in whole body and fillet were observed at each incremental level of dietary fish oil. Percentages of n-3 and n-3 highly unsaturated fatty acids in fillet of fish fed the control and 3% fish oil diets decreased with increasing feeding periods, whereas those of fish fed 6 or 9% added fish oil diets remained stable or increased. Ratios of n-3/n-6 were statistically comparable throughout the 15-wk feeding. When expressed in terms of mg/g of fillet, the highest concentration of n-3 was obtained in fillets of fish fed the 9% added fish oil diet for 15 wk. There is evidence that high levels of omega-3 highly unsaturated fatty acids (n-3 HUFA), which consist mainly of eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3), play vital roles in human nutrition, disease prevention, and health promotion (Sidhu 2003). They provide a protective effect in minimizing the development of several chronic degenerative diseases and have a therapeutic effect in certain cases (Magaro et al. 1988; Okuyama et al. 1997; Belch and Muir 1998; Horrocks and Yeo 1999). Humans cannot synthesize de novo n-3 HUFA, and these must be obtained through the diet. Marine organisms are the primary sources of these fatty acids (FAs) available to humans. As the general public becomes aware of the health benefits of consuming seafood high in n-3 HUFA, the content of these FAs in aquaculture products could become a major factor in determining consumer acceptance in the future. Production of channel catfish, Ictalurus punctatus, has become the largest aquaculture enterprise in the USA. To ensure continued growth of this industry, quality of channel catfish products has to be maintained and improved, particularly with regard to the quality of lipids. Fish and shellfish ingest and accumulate n-3 FAs through the food chain from algae and phytoplankton, the primary producers of n-3 FAs. Most vegetable oils and fats from domestic animals contain high levels of n-6 FAs and low concentrations of n-3 HUFA. Because of differences in essential FA requirements, cultured freshwater fish, including channel catfish, are commonly fed grain–soybean meal feeds high in n-6 FAs, whereas marine fish are fed diets rich in n-3 HUFA (NRC 1993). However, it has been shown that FA composition of fat in fish tissues is influenced by dietary FA composition (Stickney and Andrews 1971; Gatlin and Stickney 1982; Janncke et al. 1988; Chen et al. 1995; Grigorakis et al. 2002). Channel catfish fed diets supplemented with fish oil had significantly increased concentrations of n-3 HUFA (AbdelAty Mohamed 1989; Li et al. 1994; Fracalossi and Lovell 1995; Manning and Li 2002), and the tissue concentrations of n-3 HUFA are 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 38, No. 4 December, 2007 Copyright by the World Aquaculture Society 2007