Asthma, Performance and Omega-3s in Racing Thoroughbreds

Included in the Grayson-Jockey Club Research Foundation's 2021 funded research, www.grayson-jo..., is a project from Dr. Laurent Couetil, Purdue University that investigate the variability of asthma severity in horses racing across the US, its effect on performance and determine if omega-3 PUFA supplementation is beneficial.
Equine asthma is an important cause of poor racing performance. A study of Thoroughbreds racing in Indiana demonstrated that 80% of examined horses had mild asthma. It is not known if asthma is equally common among horses racing elsewhere in the US or if the type of inflammation varies based upon climate or geographic location.
The effect of asthma upon racing performance varies with the type of inflammation present. The airways of asthmatic horses may have an increase in one or any combination of inflammatory cells: mast cells, neutrophils, or, rarely, eosinophils. In Indiana Thoroughbreds, mast cell inflammation has roughly twice the negative effect on racing performance that neutrophil inflammation does. The degree of mast cell inflammation varies with fungal exposure, while the degree of neutrophil inflammation is related to overall dust exposure. Thus, it is likely that different environmental triggers lead to different types of inflammation and is likely to vary with different climates and geographic regions.
Because reducing exposure to organic dust and its fungal components is important to prevent and treat equine asthma, low-dust forages such as steamed hay, pelleted hay, and haylage have been investigated. Haylage appears to offer additional benefit beyond that of reduced dust exposure alone, presumably due to a more beneficial nutritional profile higher in omega-3 polyunsaturated fatty acids (omega-3 PUFA). Omega-3 PUFA work to resolve inflammatory processes and offer a potential natural way to treat and prevent asthma in the equine athlete. However, haylage is not readily available in most US locations and can carry a risk of botulism. Rather than changing a horse’s forage, adding a dietary supplement high in omega-3 PUFA would be an attractive alternative.
Therefore, this study has 3 main goals: 1. Investigate the variability of asthma severity and type in horses racing in differing climate conditions and geographic regions across the US, 2. Examine the effect of asthma upon racing performance, and 3. Determine if omega-3 PUFA supplementation can reduce the asthmatic inflammatory response.
Importance to the Equine Industry: Equine asthma, formerly referred to as inflammatory airway disease, is extremely common in racehorses, with up to 80% of horses racing in Indiana affected. It is unknown whether the frequency of asthma diagnosis in actively racing horses or the type of inflammation diagnosed varies across the US.
While asthma is very common in racehorses, signs of the disease are subtle and may not be recognized in all cases. When asthma is diagnosed, racehorses are commonly treated with corticosteroids, bronchodilators, antimicrobials, and nebulized substances, despite a lack of evidence to support their effectiveness. In addition, these treatments carry the risks of violation of medication statutes, adverse side effects, drug resistance, and negative public perception.
Therefore, means of managing equine asthma with natural dietary products are of great interest to veterinarians, trainers, and racing boards alike. Reducing horses’ exposure to dust is often limited by real-world constraints: haylage is not universally available and carries the risk of botulism, steaming hay is labor-intensive, and feeding pelleted hay can be costly while increasing the risk of unwanted behaviors in stalled horses, such as cribbing. Dietary supplementation that corrects the relative deficiency of omega-3 PUFA in stabled horses fed dry hay may aid in the resolution of airway inflammation, reduce the use of potentially harmful drugs, and improve the welfare of not only racing horses, but equine athletes in general.