Airway Lipid Mediators in Horses: Baseline Bronchoalveolar Lavage Fluid Profiles and Effects of EPA and DHA-rich Microalgae Oil Supplementation.

We investigated how dietary omega-3 polyunsaturated fatty acids (n-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) affect airway inflammation, bronchoalveolar lavage fluid (BALF) lipid mediators and red blood cell fatty acids in horses. Increased BALF neutrophils are a hallmark of airway inflammation, commonly associated with equine asthma. The long-chain n-3 PUFAs EPA and DHA are essential nutrients and precursors of specialized pro-resolving mediators (SPMs) that regulate inflammatory responses. In this prospective field trial, we assigned horses to three diets, including an EPA- and DHA-enriched feed, for 7.5 weeks. We collected blood samples and BALF before and after the feeding period. We assessed BALF inflammatory cells by cytology and lipid mediators by liquid chromatography-tandem mass spectrometry, and red blood cell fatty acids by gas chromatography of fatty acid methyl esters. We analyzed the data using linear mixed-effects models. EPA and DHA supplementation was associated with reduced BALF neutrophil percentages, whereas the levels increased in unsupplemented controls. This was accompanied by increased red blood cell EPA and DHA and the n-3/n-6 PUFA ratio. This study provides one of the first LC-MS/MS-based descriptions of BALF lipid mediator profiles in clinically healthy horses, characterized by a predominance of DHA-derived lipid mediators and pathway markers. The supplementation primarily influenced precursor availability rather than downstream SPM production. BALF maresins appeared responsive to seasonal variation.