Dust exposure and pulmonary inflammation in Standardbred racehorses fed dry hay or haylage: A pilot study.

This research looks at the impact of dust exposure, linked to feeding dry hay, on racehorses’ lung health and inflammation. The study suggests that feeding horses with haylage – a type of forage for animals – as opposed to dry hay, can lead to significantly lower dust exposure and therefore less airborne irritant-induced airway inflammation.

Study design and methodology

• Seven Standardbred racehorses were used for this study over a span of six weeks whilst they were actively training on a treadmill.
• These horses were divided into two groups: those fed alfalfa hay and those given a mix of grass-alfalfa haylage.
• Horses’ dust exposure was measured at their breathing zone, assessing the concentration of respirable dust they took in.
• The study also measured levels of endotoxins and β-glucan, components found in dust which can contribute to inflammation, in the respirable dust.
• Bronchoalveolar lavage fluid (BALF), a tool to measure lung health, was collected at different points throughout the six weeks (baseline, week 2, week 4, and week 6) to assess for airway cytology and inflammatory cytokine concentrations.

Findings and conclusion

• The study found that horses fed haylage had considerably lower respirable dust and β-glucan exposures compared to those fed hay.
• Horses that were fed haylage showed a decrease in the proportion of neutrophils, a type of white blood cell and an indicator of inflammation, in their BALF at the second and sixth week of the study period.
• By the end of the study, horses fed haylage had less airway inflammation, as measured by BALF neutrophilia, compared to those fed hay.
• There was also an increase in the interleukin-4 concentration, an anti-inflammatory protein, from baseline in horses fed hay.
• The study concludes that switching from feeding hay to haylage in training horses can lead to lower exposure to airborne irritants and potentially reduce lung inflammation.