Effects of mixed polyphenol supplementation on lower airway inflammation in horses with Equine Asthma Syndrome.

Background: Equine Asthma Syndrome (EAS) is a chronic inflammatory respiratory disease of adult horses. While dietary polyphenols have shown anti-inflammatory effects in human asthma, their use in equine asthma has not been studied.

Aims: To evaluate the effects of a mixed polyphenol supplement on systemic and pulmonary inflammation, bronchoalveolar lavage (BAL) cytology, and clinical respiratory signs in healthy and asthmatic horses. We hypothesized that polyphenol supplementation would decrease systemic and pulmonary inflammation in both healthy and asthmatic horses and would improve BAL cytology and clinical respiratory signs in asthmatic horses.

Methods: In Part One, 18 horses (eight healthy, 10 asthmatic) received a daily mixed polyphenol supplement for 6-8 weeks. Physical examination, BAL cytology, and cytokine concentrations in serum and BAL fluid were assessed before and after supplementation. In Part Two, 10 asthmatic horses were randomized into supplemented and control groups (n = 5/group). After 4 weeks on a low-dust diet with or without supplementation, airway inflammation was exacerbated using dusty hay for 4 weeks. Clinical respiratory signs, rebreathing exam findings, and pulmonary inflammation were assessed.

Results: In asthmatic horses in Part One, BAL % neutrophils and BAL IL-6 concentrations significantly decreased post-supplementation (P = 0.02; 95 % CI = 93.86 to 913.2 pg/ml), and a greater decrease in BAL IL-10 was observed in asthmatic compared to healthy horses (P = 0.02; 95 % CI = -22.4 to -0.01). In Part Two, the proportion of horses with abnormal rebreathing exams differed significantly between groups (P = 0.002; 95 % CI = 0.11 to 0.41), and supplemented horses had significantly lower respiratory rates (P = 0.008; 95 % CI = -18.0 to -4.0).

Conclusions: Polyphenol supplementation may modulate pulmonary inflammation and improve clinical signs in mildly asthmatic horses when combined with environmental management.