Effects of soaked hay on lung function and airway inflammation in horses with severe asthma.

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.

Nebulized dexamethasone sodium phosphate in the treatment of horses with severe asthma.

BACKGROUND: A study reported low systemic availability of injectable dexamethasone nebulized to healthy horses using the Flexineb mask. When used in horses with severe asthma and a different nebulizer, lack of efficacy and cortisol suppression were observed. HYPOTHESIS: Nebulized dexamethasone is as effective as PO administration for the treatment of severe asthma in horses. ANIMALS: Twelve horses with severe asthma from a research herd. METHODS: Randomized clinical trial. Horses were divided into 2 groups and received 5 mg of dexamethasone sodium phosphate by nebulization using a Flexineb mask (NE, n = 6) or PO (OR, n = 6) q24h for 7 days. Lung function and serum cortisol concentrations were evaluated at baseline, after 4 days of treatment (D4) and 1 day after the last treatment (D8). Data were analyzed using linear mixed models with Benjamini-Hochberg adjustments. RESULTS: Lung resistance significantly improved at D4 (mean decrease ± SD, -1.5 ± 0.45 cm H2O/L/s; 95% confidence interval [CI], -2; -0.6) and D8 (-1.4 ± 0.45 cm H2O/L/s; 95% CI, -2.4; -0.5) compared to baseline in the OR group only (P = .004 and .01, respectively). Serum cortisol concentration was significantly decreased at D4 and D8 for both groups (maximum decrease, -1.2 ± 0.3 µg/dL; 95% CI, -1.9; -0.6 at D4 for NE group and -2.2 ± 0.3 µg/dL; 95% CI, -2.8; -1.6 at D8 for OR group; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Oral, but not nebulized dexamethasone is an effective therapy for horses with severe asthma and both treatment modalities inhibit the hypothalamic-pituitary-adrenal axis.

Pulmonary response of severely asthmatic horses after intra-articular administration of methylprednisolone.

BACKGROUND: Intra-articular (IA) administration of corticosteroids is performed routinely in equine practice. The lung function of severe asthmatic horses has recently been shown to be improved by IA triamcinolone acetonide (TA). We therefore hypothesised that IA methylprednisolone acetate (MPA), another commonly used corticosteroids, would also decrease the airway obstruction in severe asthmatic horses. OBJECTIVES: To compare the effects of intra-articular (IA) and intramuscular (IM) methylprednisolone acetate (MPA) administration on lung function and serum cortisol levels in horses with severe asthma. STUDY DESIGN: Randomised and controlled experiments on severe asthmatic research animals. METHODS: Severe asthmatic horses in exacerbation were administered 200 mg of MPA either intramuscularly (n = 6) or via intra-articular injections in the tarsocrural joints (n = 6; 100 mg/joint). Serum cortisol concentration and pulmonary function was measured for 8 days. RESULTS: A significant decrease in pulmonary resistance in the IA group (P = .003, mean diff 1.14) on day 1 in comparison with baseline was observed. A significant decrease from baseline was also observed on serum cortisol values in the IA group 6 hours after injection (P = .001, mean diff 44.5), and at day 1 (P = .003, mean diff 45.1). MAIN LIMITATIONS: Joint health was not evaluated in the current study and the physiological response of the severe asthmatic horses might deviate from that of the milder forms of asthma. CONCLUSIONS: MPA IA administration improves the lung function of severe asthmatic horses. However, this effect was mild and of a short duration.

Effects of a propriety oiled mixed hay feeding system on lung function, neutrophilic airway inflammation and oxidative stress in severe asthmatic horses.

BACKGROUND: Hay feeding is considered the main triggering factor for airway obstruction and inflammation in severe equine asthma (SEA). Finding alternate strategies allowing hay feeding while controlling clinical signs of SEA is of importance. The Nutri-Foin Système is believed to decrease inhaled dust by incorporating soybean oil to mechanically processed hay. OBJECTIVES: We compared airflow obstruction and airway inflammation in horses with SEA fed oiled hay or alfalfa pellet regimen. STUDY DESIGN: Controlled trial in asthmatic research horses. METHODS: Twelve horses in exacerbation of SEA from a research herd were studied. Horses were fed either oiled treated hay (n = 6) or alfalfa pelleted hay (n = 6) for 3 months while being stabled. Lung function, bronchoalveolar lavage fluid cytology and serum antioxidant enzyme kinetics were sequentially evaluated. RESULTS: Pelleted hay and the hay treated with the Nutri-Foin Système similarly improved lung function, airway neutrophilia and serum antioxidant enzyme kinetics over time. MAIN LIMITATIONS: The small number of horses in each group. CONCLUSIONS: We conclude from this study that Nutri-Foin Système is an appropriate alternative to pelleted hay for the control of the airway obstruction in horses with SEA.

Efficacy of tamoxifen for the treatment of severe equine asthma.

BACKGROUND: Tamoxifen, a selective estrogen receptor modulator, decreased airway neutrophilia and improved clinical signs in an experimental model of equine asthma, and induced neutrophilic apoptosis in vitro. HYPOTHESIS/OBJECTIVES: Tamoxifen reduces airway neutrophilia and improves lung function in severe asthmatic horses. ANIMALS: Twelve severe asthmatic horses from a research herd. METHODS: Randomized controlled blinded study design. The effects of a 12-day oral treatment with tamoxifen (0.22 mg/kg, q24h) or dexamethasone (0.06 mg/kg, q24h) on lung function, endoscopic tracheal mucus score and bronchoalveolar lavage fluid cytology were compared. RESULTS: Tamoxifen significantly improved the pulmonary resistance (RL ; mean reduction of 1.15 cm H2 O/L/s [CI: 0.29-2.01, P = .007] on day 13), but had no effect on the other variables evaluated. Dexamethasone normalized lung function (mean reduction of RL of 2.48 cm H2 O/L/s [CI: 1.54-3.43, P < .0001] on day 13), without affecting airway neutrophilia. CONCLUSIONS AND CLINICAL IMPORTANCE: Results of this study do not support the use of tamoxifen at the dose studied as an antineutrophilic medication in the treatment of asthmatic horses in chronic exacerbation.