Effects of forages, dust exposure and proresolving lipids on airway inflammation in horses

OBJECTIVE To investigate the role of omega-3 polyunsaturated fatty acids (O-3)-derived proresolving lipid mediators (PRLM) in the resolution of mild airway inflammation in horses. ANIMALS 20 horses with mild airway inflammation. PROCEDURES Horses previously eating hay were fed hay pellets (low O-3 content; n = 10) or haylage (high O-3 content; 9) for 6 weeks. Dust exposure was measured in the breathing zone with a real-time particulate monitor. Bronchoalveolar lavage (BAL) was performed at baseline, week 3, and week 6. The effect of PRLM on neutrophil apoptosis and efferocytosis was examined in vitro. BAL fluid inflammatory cell proportions, apoptosis of circulating neutrophils, efferocytosis displayed by alveolar macrophages, and plasma lipid concentrations were compared between groups fed low and high amounts of O-3 by use of repeated measures of generalized linear models. RESULTS Dust exposure was significantly higher with hay feeding, compared to haylage and pellets, and equivalent between haylage and pellets. BAL fluid neutrophil proportions decreased significantly in horses fed haylage (baseline, 11.8 +/- 2.4%; week 6, 2.5 +/- 1.1%) but not pellets (baseline, 12.1 +/- 2.3%; week 6, 8.5% +/- 1.7%). At week 6, horses eating haylage had significantly lower BAL neutrophil proportions than those eating pellets, and a significantly lower concentration of stearic acid than at baseline. PRLM treatments did not affect neutrophil apoptosis or efferocytosis.