Effect of dietary lipids on fatty acid composition and hematological parameters of channel catfish Ictalurus punctatus exposed to different temperature challenges

A series of studies was conducted to determine the effects of different dietary lipid sources (menhaden oil, MO; catfish oil, CO; or beef tallow, BT) on fatty acid composition (neutral and polar), selected hematological parameters, and cold tolerance in channel catfish Ictalurus punctatus . Significant differences existed in the neutral fatty acid profile of fingerling channel catfish fed diets containing different dietary lipid sources over a 12-week feeding trial. Catfish fed the MO diet contained the highest concentrations of n-3 highly unsaturated fatty acid content (HUFA) and docosahexaenoic acid (DHA). The MO diet also increased concentrations of alpha-linolenic acid (ALA) and total unsaturation content in the polar lipids. Fish fed diets containing BT had significantly higher levels of stearic acid and oleic acid concentration than fish fed MO or CO diets. Exposure to a gradual decrease in water temperature increased monounsaturated fatty acid content within the neutral lipids of catfish fed BT and MO diets, whereas a rapid decrease in water temperature increased 18:4n-3, eicosapentaenoic acid (EPA), and DHA in fish fed BT diets, but only DHA within fish fed the CO diet. For polar lipids, total monounsaturated fatty acids increased in fish fed BT and CO diets after exposure to a gradual decrease in water temperature. A rapid decrease in water temperature increased the concentrations of DHA and n-3 HUFAs within fish fed BT, CO, or MO diets. Manipulation of dietary lipids did not mitigate effects of the temperature stress subjected to the juvenile catfish. Results from a finishing diet study indicated no differences existed between MO and CO in terms of influencing n-3 HUFA content in the juvenile channel catfish fillet. Therefore, CO may be successfully substituted for MO in formulated diets without adversely affecting n-3 HUFA content in channel catfish. In addition, I found that channel catfish contain a putative delta-6 desaturase-like gene. However, future research is needed to determine the activity level of this gene and what dietary feed ingredients would maximize the activity level of the presumptive coded enzyme to produce a more marketable product for the channel catfish industry.