Oral docosahexaenoic acid supplementation alters alveolar macrophage metabolism and protein and lipid profiles in the lower airway of healthy horses.

Oral DHA supplementation may promote anti-inflammatory alveolar macrophage polarization in horses' lower airways.

This prospective, sequential, placebo-controlled study investigated the effects of oral docosahexaenoic acid (DHA) supplementation on alveolar macrophage metabolism and bronchoalveolar lavage (BAL) fluid composition in healthy adult horses. Ten horses were enrolled, with seven completing the study. The protocol included baseline BAL collection, 45 days of placebo administration, a 14-day washout period, and 45 days of a commercially available DHA supplement (containing DHA, methylsulfonylmethane, and a mushroom blend). DHA supplementation significantly decreased the whole-blood omega-6 to omega-3 fatty acid ratio and increased the DHA to arachidonic acid ratio, confirming successful supplementation and absorption. Following DHA administration, alveolar macrophage basal and maximal respiratory capacity (oxygen consumption rate) increased, suggesting a metabolic shift toward oxidative phosphorylation. This metabolic pattern is associated with M2 (anti-inflammatory) macrophage polarization. Protein and lipid profiles in BAL supernatant were also significantly altered following DHA supplementation. Notably, BAL cytology remained unchanged across all study periods, indicating no gross inflammatory response. The study suggests that oral DHA supplementation may promote an anti-inflammatory lower airway environment in horses, potentially benefiting those with subclinical airway inflammation or those regularly exposed to environmental airway irritants, such as dust and mold in barn settings. Limitations include a small sample size (n=7 completers) and the use of a combination supplement rather than isolated DHA, making it difficult to attribute effects solely to DHA.

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