Soaking hay reduces dust exposure

EVJ continues its series on soaking hay and finding benefits. This was ineffective in my many equine asthma (hay mold allergy) patients. An earlier study by EVJ (see other topics) recommended a 45-minute soak time. Perhaps we did not soak long enough? This study says it reduced exposure by 50%, is that enough? Earlier studies showed soaking did not reduce the mold spore concentration in the trachea. I suspect that the severity of the allergy, the contamination level in the hay, and other factors like how the hay is fed all affect the outcome. If you do decide to try soaking for your EA-affected horse use the 45-minute recommendation. We have more effective treatment and control methods in the article.
DrO

A wearable real-time particulate monitor demonstrates that soaking hay reduces dust exposure
Equine Vet J. 2024 Oct 27. doi: 10.1111/evj.14425. Online ahead of print.
Authors
Kathleen M Ivester 1 , Ji-Qin Ni 2 , Laurent L Couetil 1 , Thomas M Peters 3 , Marcus Tatum 3 , Lynn Willems 1 , Jae Hong Park 4
Affiliations

1 College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA.
2 Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, Indiana, USA.
3 Department of Occupational and Environmental Health, University of Iowa, Iowa City, Iowa, USA.
4 School of Health Sciences, Purdue University, West Lafayette, Indiana, USA.

PMID: 39463012
DOI: 10.1111/evj.14425

Abstract

Background: Affordable particulate matter (PM) monitors suitable for use on horses will facilitate the evaluation of PM mitigation methods and improve the management of equine asthma.

Objective: Calibrate a real-time wearable PM monitor (Black Beauty [BB]) and compare the PM exposures of horses fed dry or soaked hay.

Study design: Laboratory calibration; complete cross-over feed trial.

Methods: Side-by-side sampling with BB monitors and tapered element oscillating microbalances (TEOMs) was performed under varying concentrations of PM from alfalfa hay. Linear regression was used to derive a calibration formula for each unit based on TEOM PM measurements. Precision was evaluated by calculating the coefficient of variation and pairwise correlation coefficients between three BB monitors. PM exposure was measured at the breathing zone of 10 horses for 8 h after they were fed dry or soaked hay. Repeated measures generalised linear models were constructed to determine the effect of hay treatment and measurement duration (initial 20-min vs. 8-h) upon exposure to PM with diameters smaller than or equal to 10 μm (PM10) and 2.5 μm (PM2.5).

Results: BB monitor PM2.5 and PM10 measurements were linearly correlated with TEOM data (coefficient of determination r2 > 0.85 and r2 > 0.90 respectively), but underestimated PM2.5 mass concentrations by a factor of 4 and PM10 concentrations by a factor of 44. Measures from the three BB monitors had a coefficient of variation <15% and pairwise r > 0.98. Feeding soaked hay significantly reduced average PM2.5 exposures (20-min: dry: 160 μg/m3, soaked: 53 μg/m3, p < 0.0001; 8-h: dry: 76 μg/m3, soaked: 31 μg/m3, p = 0.0008) and PM10 exposures (20-min: dry: 2829 μg/m3, soaked: 970 μg/m3, p < 0.0001; 8-h: dry: 1581 μg/m3, soaked: 488 μg/m3, p = 0.008).

Main limitations: No health outcome measures were collected.

Conclusions: With appropriate corrections, the BB monitor can be used to estimate horse PM exposure. While 20-min measurements yielded higher estimates of exposure than 8-h measurements, both intervals demonstrate that soaking hay reduces PM exposures by more than 50%.

Keywords: asthma; calibration; horse; optical sensor; organic.