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

The research sought to understand the role of omega-3 fatty acid-derived proresolving lipid mediators (PRLM) in resolving mild airway inflammation in horses. The study found that horses that were fed haylage displayed a greater decrease in airway inflammation than those fed pellets, with this improvement not being associated with increased plasma omega-3 concentrations.

Study Design and Methodology

• A group of 20 horses with mild airway inflammation were selected for the study. These horses were previously fed hay, then they were split into two groups. One group was switched to hay pellets (low omega-3 content; n = 10) and the other to haylage (high omega-3 content; n = 9) and fed for 6 weeks.
• The researchers also measured dust exposure in the breathing zone of the horses using a real-time particulate monitor.
• Bronchoalveolar lavage (BAL), a method of obtaining a sample of lung tissue, was carried out at the start of the study, in the third week and the sixth week.
• The effect of PRLM on neutrophil (type of white blood cell) apoptosis (programmed cell death) and efferocytosis (the process by which dying or dead cells are removed) was tested in the lab.
• The team compared various metrics between horses fed on low and high amounts of Omega-3 including inflammatory cell proportions in the BAL fluid, apoptosis of circulating neutrophils, and efferocytosis by alveolar macrophages, alongside plasma lipid concentrations.

Results

• The level of dust exposure was significantly higher when feeding hay as opposed to haylage and pellets. Dust exposure was equal between haylage and pellet feeding.
• There was a significant decrease in the BAL fluid neutrophil proportions in horses fed with haylage, but not in those fed with pellets. By week 6, horses eating haylage had considerably lower BAL neutrophil proportions and a significantly lower concentration of stearic acid than those eating pellets.
• The treatments involving PRLM did not affect apoptosis or efferocytosis of neutrophils.

Conclusion

• The research suggests that despite similar reductions in dust exposure, horses fed on haylage showed a significant decrease in airway inflammation compared with those fed on pellets. This decrease, however, was not associated with an increase in plasma omega-3 concentrations.
• The researchers concluded that feeding haylage improves horses’ airway inflammation beyond what is achieved by reduced dust exposure. However, the mechanism behind this improvement remains unclear and requires further investigation.