Revisiting Eicosapentaenoic Acid & Docosahexaenoic Acid Recommendations for Healthy Siberian Huskies at Maintenance: Greater Dietary EPA & DHA Increase Plasma Lipid Incorporation & Reduce α-Tocopherol Concentrations

Recent evidence suggests that higher-than-recommended intakes of long-chain n-3 polyunsaturated fatty acids (PUFA), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are both safe and effective in supporting health conditions such as inflammatory diseases in adult humans. For adult dogs at maintenance, the National Research Council (NRC, 2006) recommends a safe upper limit of EPA+DHA of 0.37 g/kg body weight (BW)0.75, a value based on limited evidence. This study aimed to investigate how low, moderate and high dietary intakes of EPA+DHA affected oxidative balance through α-tocopherol and malondialdehyde (MDA) concentrations, lipid incorporation into circulating phospholipid fractions, and serum cytokines in healthy adult dogs over 8 weeks. Twenty-seven client-owned dogs were enrolled and, following a 4-week diet acclimation phase, were allocated into three groups balanced for age and BW and then randomly assigned to 1 of 3 dosage groups, consisting of 0.03 g/kg BW0.75 (LOW) of EPA+DHA, 0.45 g/kg BW⁰·⁷⁵ (MOD), and 0.71 g/kg BW⁰·⁷⁵ (HIGH). Fasted blood samples were collected at weeks 0, 4, and 8 to evaluate serum fatty acid (FA) composition within circulating phospholipid fractions, whole blood α-tocopherol, malondialdehyde (MDA), and cytokine concentrations. Data were analyzed using PROC GLIMMIX in SAS, with dog treated as a random effect, week as a repeated measure, and dosage group (DG), week, sex, and their interactions as fixed effects. In serum phosphatidylcholine (PC) and lysophosphatidylcholine (LysoPC) fractions, EPA and DHA incorperation increased from baseline to week 4 across all dosage groups, with no changes observed between weeks 4 and 8. Total FA analysis showed that dietary EPA+DHA increased total n-3 PUFA and reduced total n-6 PUFA, with both the MOD and HIGH being greater than the LOW treatment. Whole blood α-tocopherol concentrations showed a DG × week interaction (p = 0.034), with the LOW group (5.82 µg/mL) maintaining higher concentrations at week 8 than the HIGH group (3.52 µg/mL) and not differing from the MOD group (5.00 µg/mL). Overall, increasing dietary EPA+DHA intake in adult dogs enriched circulating and membrane-associated n-3 PUFA pools while maintaining MDA and inflammatory cytokine concentrations despite reduced α-tocopherol concentrations. This suggests that higher EPA+DHA intakes were well tolerated over the 8-week study period when interpreted alongside antioxidant status.