Effect of dietary omega-3 fatty acid source on plasma and red blood cell membrane composition and immune function in yearling horses.

The research investigation evaluates the effects of two sources of dietary omega-3 fatty acids – fish oil and flaxseed, on the composition of plasma and red blood cell (RBC) fatty acids and immune response in yearling horses. The study suggests that omega-3 sourced from fish oil affectively increases omega-3 content in plasma and RBC more than flaxseed, however, supplementing with either fish oil or flaxseed led to a more pronounced early inflammatory response in horses.

Study Design and Methodology

• In this experiment, 18 Quarter Horse yearlings were divided into three groups and each group was given a different treatment: fish oil supplement, flaxseed supplement, or no supplement (control).
• While fish oil provided eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), flaxseed supplement contained alpha-linolenic acid.
• The horses were on these diets for 70 days, during which they were also allowed free access to bahiagrass pasture and were individually fed a grain mix concentrate.
• The fish oil and flaxseed supplements were mixed into the concentrate in such amounts so as to provide 6 grams of total omega-3 per 100 kilograms of their body weight.
• Blood samples were collected from the horses to determine the FA composition of their plasma and RBCs and also to isolate peripheral blood mononuclear cells for assessing immune response.
• Lymphocyte proliferation was determined by stimulating peripheral blood mononuclear cells with concanavalin A and phytohemagglutinin (PHA) and PGE (2) production was measured post lipopolysaccharide challenge.
• In vivo inflammatory response was evaluated on day 70 by measuring the thickness of the skin and the area of swelling after an intradermal injection of PHA.

Key Findings

• Body weight gain was not affected by the dietary treatment applied.
• Horses that consumed fish oil had an increase in EPA, DHA, and the sum of omega-3 in the plasma and RBC as compared to those fed with flaxseed and control.
• Flaxseed and fish oil supplementation resulted in a larger increase in skin thickness and area of swelling after PHA injection than the control group.
• Although both the flaxseed and fish oil groups received similar amounts of n-3 fatty acids, fish oil had a greater impact on plasma and RBC omega-3 fatty acid content than did flaxseed.

Implications

• Overall, the study suggests that supplementing with fish oil and flaxseed may lead to a more pronounced early inflammatory response in horses. The increased inflammatory response might be an indication of a boosted immune response triggered by the omega-3 fatty acids in both fish oil and flaxseed supplements.
• The augmented swelling and skin thickness in horses supplemented with flaxseed and fish oil might be indicative of an immune system that is more alert to intrusion, hence a higher, quicker immune response post-inflammation stimulation.
• The findings also underline the role of omega-3 sources in modifying plasma and RBC n-3 FA content, and the superiority of fish oil in achieving this compared to flaxseed in the amounts administered in this study.