PSIX-6 Algal oil as an alternative source of docosahexaenoic acid in feline diets

Abstract The global demand for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation by humans and their necessity in companion animal foods has raised questions related to environmental sustainability and nutrient content of fish oil. The combination of reported diminishing EPA and DHA content in fish oil and the forecasting of a significant decline in global fish stocks over the next decade make it critical to consider alternative sources of omega-3 fatty acids to reduce dependence on fish harvests. Cultured algal oil has been identified as a promising and viable alternative to fish-based oils. As such, the purpose of this study was to determine the inclusion level of algal oil in cat foods necessary to deliver the same serum concentrations of DHA provided from fish oil. Cats (n = 26) were first fed a control food formulated to avoid ingredients that contain long chain omega-3 fatty acids [ɑ-linolenic (ALA), EPA, and DHA] for 5 wk, to establish a baseline serum concentrations of these fatty acids. Cats were then randomized into two groups, and fed test foods containing either fish oil or algal oil in sequential increasing levels of DHA (0.2%, 0.4%, and 0.6%) for 5-wk periods each. Blood was analyzed for serum DHA and EPA concentrations after each of these feeding periods. A regression analysis was used to calculate a bioequivalence factor between fish oil and algal oil inclusion levels. There was no difference (P > 0.05) in intake or body weight between cats consuming diets containing algal oil or fish oil. Analysis of serum fatty acid concentrations showed that increasing fish and algal oil had no effect (P > 0.05) on serum linolenic acid, ALA, or arachidonic acid; however, increasing fish and algal oil did have an effect on DHA such that serum DHA was increased at similar rates as fish oil (P = 0.050) and algal oil (P = 0.026) levels were increased in the diet. Although increasing levels of fish and algal oil both increased serum EPA concentrations (P < 0.001), fish oil increased serum EPA to a greater extent than algal oil when fed at all levels. Overall, these data indicate that inclusion of algal oil is a good alternative dietary source of DHA, but less of EPA, and that algal oil will need to be added to the diet in higher concentrations to achieve similar serum EPA concentrations as fish oil.