75 Re-evaluating recommendations for Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) for adult dogs: A dose-response study on antioxidant status.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are two common and beneficial n-3 fatty acids for dogs. The minimum required dose for adult dogs at maintenance has not been established, but the National Research Council (NRC) provides a combined recommended allowance (RA) for EPA+DHA of 0.03 g/kg body weight (BW)⁰·⁷⁵ and safe upper limit (SUL) of 0.37 g/BW⁰·⁷⁵. The SUL is based on findings in geriatric Beagles (9.5–11.5 years old), where supplementation at 0.45 g/BW⁰·⁷⁵ EPA+DHA resulted in lower α-tocopherol concentrations and higher lipid peroxidation. However, similar studies have not been conducted in healthy adult dogs, nor has a broader evaluation of oxidative balance been performed. To address this gap, an 8-week dose-response study was conducted to evaluate how feeding graded inclusions of dietary EPA+DHA may impact lipid metabolism of healthy, adult dogs. We hypothesized the RA minimizes lipid peroxidation and antioxidant depletion but may not fully maximize potential anti-inflammatory benefits, while higher doses may enhance immune benefits but may also increase oxidative stress and antioxidant depletion. Twenty-seven client-owned dogs (25 Siberian Huskies and 2 Alaskan Huskies) participated, consisting of 13 females (4 intact, 9 spayed) and 14 males (3 intact, 11 neutered), aged 1-12 years with a mean age of 6.9 ± 5.8 years and a mean BW of 21.5 ± 6.8 kg (mean ± SD). Following a 4-week acclimation with once-daily feeding at 15:00 with a commercial extruded diet, dogs were blocked by age and BW before random assignment to one of three dietary groups. All dogs were fed the same low-fat experimental diet (39.8% crude protein, 13.8% crude fat, 3.0% crude fibre). The diet was supplemented with fish oil (containing 0.53g EPA and 0.38g DHA per mL) to achieve daily EPA+DHA intakes of 0.03 g/BW⁰·⁷⁵ (LOW), 0.45 g/BW⁰·⁷⁵ (MOD), and 0.71 g/BW⁰·⁷⁵ (HIGH). Feed intake was adjusted to maintain BW throughout the study period. Fasted blood samples were collected at weeks 0, 4, and 8 to assess serum fatty acid profile, lipid fractions, inflammatory cytokines, α-tocopherol, and malondialdehyde (MDA). Data were analyzed using PROC GLIMMIX in SAS, where dog was treated as a random effect, week as a repeated measure, and dose of EPA+DHA as a fixed effect. Statistical significance was declared at P≤0.05. Serum α-tocopherol concentrations were comparable across all groups at week 0 and increased similarly among groups at week 4 (p< 0.01). Dogs fed HIGH had lower α-tocopherol concentrations than LOW group (p< 0.05) but did not differ from MOD group (p=0.42) at week 8, indicating EPA+DHA intake is related to antioxidant depletion. These findings offer valuable insights into the impact of EPA and DHA supplementation on oxidative balance and may help refine current NRC recommendations and inform best practices for dietary inclusion.