Dust exposure and pulmonary inflammation in Standardbred racehorses fed dry hay or haylage: A pilot study.
Authors: Olave C J, Ivester K M, Couetil L L, Kritchevsky J E, Tinkler S H, Mukhopadhyay A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Dust Exposure and Airway Health in Racehorses Respirable dust from hay is a well-recognised trigger for airway inflammation in performance horses, yet practical evidence comparing forage types during active training has been limited. Researchers fed seven Standardbred racehorses either dry alfalfa hay or grass-alfalfa haylage over six weeks whilst measuring dust exposure at the breathing zone, along with airway cytology and inflammatory markers from bronchoalveolar lavage fluid collected at baseline, weeks 2, 4, and 6. Horses fed haylage were exposed to approximately two-thirds less respirable dust (0.02 versus 0.06 mg/m³) and β-glucan (69 versus 160 pg/m³) than those receiving hay; correspondingly, neutrophil proportions in airway fluid declined significantly in the haylage group from 2.2% to 0.7% by week 6, whilst the hay-fed horses showed persistently elevated neutrophilia at 4.0%. Additionally, interleukin-4 concentrations—a marker of inflammatory response—increased five-fold in hay-fed horses but remained suppressed in the haylage group, suggesting a protective anti-inflammatory effect. For practitioners managing performance horses prone to recurrent airway disease or those in intensive training programmes, these findings provide quantifiable evidence that haylage feeding can substantially reduce the dust-driven inflammatory burden on the respiratory tract, potentially improving both clinical outcomes and training tolerance.
Read the full abstract on PubMed
Practical Takeaways
- •Feeding haylage instead of dry hay can reduce respirable dust and endotoxin exposure by 60-70%, with measurable benefits for airway health in training horses
- •Horses transitioned to haylage show reduced airway neutrophilia within 2-6 weeks, suggesting improved respiratory status during intense training
- •For racehorses with recurrent airway obstruction or dust sensitivity, haylage should be considered as a practical management tool to mitigate environmental irritants and inflammation
Key Findings
- •Respirable dust exposure was 67% lower in horses fed haylage versus hay (0.02 vs 0.06 mg/m³, P=0.03)
- •β-glucan exposure was 57% lower in haylage-fed horses (69 vs 160 pg/m³, P=0.02)
- •BALF neutrophil proportions decreased significantly in haylage-fed horses from baseline 2.2% to week 6 0.7% (P=0.03)
- •By week 6, haylage-fed horses had significantly lower airway neutrophilia than hay-fed horses (4.0%, P=0.0004)