Soaked hay on lung function and airway inflammation in horses

Because of the difficulties getting up hay with low enough moisture, equine asthma was common in my practice in NC. Soaking hay was not an effective prevention for acute exacerbations. This paper suggests we were not soaking long enough and that a 45-minute soak would help. For other suggestions, see the article above.
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Effects of soaked hay on lung function and airway inflammation in horses with severe asthma
J Vet Intern Med. 2023 Nov 6. doi: 10.1111/jvim.16919. Online ahead of print.
Authors
Roxane Westerfeld 1 , Flavie Payette 1 , Valérie Dubuc 1 , Estelle Manguin 1 , Khristine Picotte 1 , Guy Beauchamp 2 , Christian Bédard 3 , Mathilde Leclere 1
Affiliations

1 Department of Clinical Sciences, Faculté de Médecine Vétérinaire, Université de Montréal, Quebec, Canada.
2 Faculté de Médecine Vétérinaire, Université de Montréal, Quebec, Canada.
3 Department of Pathology and Microbiology, Faculté de Médecine Vétérinaire, Université de Montréal, Quebec, Canada.

PMID: 37930110
DOI: 10.1111/jvim.16919

Abstract

Background: Reducing inhaled dust particles improves lung function in horses with severe asthma. Soaked hay is commonly used by owners, but its efficacy in improving lung function and inflammation has not been documented.

Objectives: To measure the effects of soaked hay and alfalfa pellets in horses with severe asthma.

Animals: Ten adult horses with severe asthma from a research colony.

Methods: Prospective controlled trial. Horses in clinical exacerbation were housed indoors and allocated to be fed either soaked hay (n = 5) or alfalfa pellets (n = 5) for 6 weeks. Soaked hay was immersed for 45 minutes and dried out hay was discarded between meals. Pulmonary function and clinical scores were measured before and after 2, 4, and 6 weeks. Tracheal mucus scores and bronchoalveolar lavages were performed before and after 6 weeks. Lung function was analyzed with a linear mixed model using log-transformed data.

Results: Lung resistance decreased from (median (range)) 2.47 (1.54-3.95) to 1.59 (0.52-2.10) cmH2 O/L/s in the pellets group and from 1.89 (1.2-3.54) to 0.61 (0.42-2.08) cmH2 O/L/s in the soaked hay group over the 6-week period for an average difference of 1.06 cmH2 O/L/s for pellets (95% confidence interval [95% CI]: 0.09-2.04, P = .03, not significant after correction) and 1.31 cmH2 O/L/s for soaked hay (95% CI: -0.23 to 2.85, P < .001, significant). Conclusion and clinical importance: Soaked hay can control airway obstruction in horses with severe asthma. The strict protocol for soaking and discarding dried-out hay in this study could however be considered too great of an inconvenience by owners. Keywords: equine; heaves; inflammatory airway disease; recurrent airway obstruction. © 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.