Effects of low-dust forages on dust exposure, airway cytology, and plasma omega-3 concentrations in Thoroughbred racehorses: A randomized clinical trial.
Authors: Olave Carla J, Ivester Kathleen M, Couetil Laurent L, Burgess John, Park Jae Hong, Mukhopadhyay Abhijit
Journal: Journal of veterinary internal medicine
Summary
# Editorial Summary: Low-Dust Forages and Airway Health in Racehorses Dust-induced airway inflammation is endemic in racehorses, yet the interplay between forage type, dust exposure, and inflammatory biomarkers remains poorly characterised in clinical settings. This randomised trial assigned 43 Thoroughbreds to six weeks of dry hay, steamed hay, or haylage, measuring respirable dust concentrations in the breathing zone, bronchoalveolar lavage fluid (BALF) cytology at baseline, week 3, and week 6, and plasma lipid profiles including omega-3 polyunsaturated fatty acids and specialised pro-resolving mediators. Both steamed hay and haylage significantly reduced respirable dust exposure compared with conventional dry hay (0.053–0.056 mg/m³ versus 0.081 mg/m³), but haylage proved uniquely effective at dampening airway neutrophilia: BALF neutrophil proportions fell from 5.1% to 3.0% by week 6, whereas dry hay-fed horses showed proportions of 6.3%. Critically, only haylage elevated the eicosapentaenoic acid-to-arachidonic acid ratio—a marker of the anti-inflammatory lipid environment—rising from 0.34 to 0.51, substantially outperforming both hay variants. For practitioners managing respiratory-compromised racehorses, haylage emerges as superior to steamed or dry hay in reducing both dust burden and airway inflammation through dual mechanisms of lower dust generation and improved lipid profiles conducive to resolution of inflammation.
Read the full abstract on PubMed
Practical Takeaways
- •Switch racehorses from dry hay to either steamed hay or haylage to reduce respirable dust exposure by 25-35%, with particular benefits for horses showing airway inflammation
- •Haylage feeding is superior to steamed hay for addressing mild asthma in racehorses by improving plasma omega-3 ratios and reducing airway neutrophil proportions; consider this dietary intervention for horses with exercise-induced airway disease
- •Dust-related airway inflammation in racehorses may be modifiable through forage selection alone within 6 weeks, offering a practical non-pharmaceutical management strategy
Key Findings
- •Respirable dust exposure was significantly higher in horses fed dry hay (0.081 mg/m³) compared to steamed hay (0.056 mg/m³) or haylage (0.053 mg/m³)
- •Haylage reduced BALF neutrophil proportions from 5.1% at baseline to 3.0% at week 6, whereas dry hay increased proportions to 6.3%
- •Horses fed haylage for 6 weeks increased eicosapentaenoic acid to arachidonic acid ratios to 0.51 compared to 0.34 at baseline and 0.24-0.25 in hay-fed groups
- •Only haylage produced both reduced dust exposure and improved anti-inflammatory to pro-inflammatory lipid ratios within 6 weeks