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

Abstract

OBJECTIVE To investigate the role of omega-3 polyunsaturated fatty acids (Ω-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 Ω-3 content; n = 10) or haylage (high Ω-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 Ω-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. CLINICAL RELEVANCE Despite similar reduction in dust exposure, horses fed haylage displayed greater resolution of airway inflammation than those fed pellets. This improvement was not associated with increased plasma Ω-3 concentrations. Feeding haylage improves airway inflammation beyond that due to reduced dust exposure, though the mechanism remains unclear.

Effects of low‐dust forages on dust exposure, airway cytology, and plasma omega‐3 concentrations in Thoroughbred racehorses: A randomized clinical trial

“…This study documents the beneficial effects of low‐dust forage feeding on BALF cytology in racehorses with naturally occurring airway inflammation. Horses fed haylage has a rapid reduction in BALF neutrophil proportions, while those fed hay pellets do not, despite equivalent PM exposures 44 . When fed haylage, horses with severe asthma can maintain clinical remission and low BAL neutrophil proportions (<10%) for months 45 .…”

“…Horses fed haylage has a rapid reduction in BALF neutrophil proportions, while those fed hay pellets do not, despite equivalent PM exposures. 44 When fed haylage, horses with severe asthma can maintain clinical remission and low BAL neutrophil proportions (<10%) for months. 45 A similar beneficial effect was observed in horses with mild asthma in the current study.…”

Lipids in Equine Airway Inflammation: An Overview of Current Knowledge

“…In horses, haylage feeding causes greater resolution of airway inflammation than other low-dust forage products (pelleted hay and steamed hay) [ 58 , 115 ]. In one study, haylage increased the ratio of anti-inflammatory to proinflammatory FAs in the horse’s plasma, where the EPA:AA ratios were higher in horses after eating haylage for 6 weeks compared with baseline or horses eating steamed or dry hay [ 58 ].…”