FISH OIL IMPROVES AIRWAY INFLAMMATION, RACING PERFORMANCE

April 15, 2026 By Kentucky Equine Research

Researchers from Purdue University recently reported that supplementing with fish oil alone benefits horses with neutrophilic asthma even without reducing dust exposure.^*

Under most circumstances, one of the most important ways of managing horses with equine asthma, also referred to as inflammatory airway disease (IAD), is reducing exposure to dust and other airborne particulate material. The main sources of dust in a horse’s breathing zone, the two-foot sphere surrounding a horse’s nostrils, are hay and bedding.

“This is why experts recommend soaking or steaming hay and minimizing the time that asthmatic horses are stabled,” explained Catherine Whitehouse, M.S., a nutritionist for Kentucky Equine Research. “In addition to reducing dust, one study also demonstrated that soaking hay improves lung function in asthmatic horses.”^**

Be cautious, however, because soaking hay, particularly for an extended period of time, can leach nutrients and produce a nutritional void if not addressed by the concentrate portion of the diet.

Horses fed soaked hay should receive a feed that supplies quality protein and a complete source of vitamins and minerals when fed as recommended,” recommended Whitehouse.

As an alternative to hay soaking, the Purdue researchers reported that low-dust haylage improves airway inflammation.⁺

“In addition to reducing an asthmatic horse’s exposure to dust, the most frequent consensus guidelines on inflammatory airway disease also recommend supplementing horses with omega-3 fatty acids,” said Whitehouse.⁺⁺

To determine if omega-3 fatty acids alone reduce asthma, without environmental changes like feeding low-dust hay or haylage, Purdue researchers conducted a double-masked controlled clinical trial including 80 clinically healthy Thoroughbred racehorses housed at four separate locations. Horses received either an omega-3 enriched fatty acid supplement or corn oil for four weeks. A bronchoalveolar lavage was performed at the end of the study period.

Bronchoalveolar fluid analysis revealed that neutrophils, a type of inflammatory white blood cell, decreased significantly in horses receiving the omega-3 supplement compared to the corn oil. As a secondary finding, measures of athletic performance increased in supplemented horses, such as money earned during racing.

Be certain to have your horse examined by a veterinarian if you suspect equine asthma, as other causes of respiratory issues must be ruled out. And while these results are promising, horses with this disease may also require treatment with medications and benefits of dust avoidance.

Kentucky Equine Research offers EO-3 as a direct source of the long-chain polyunsaturated fatty acids DHA and EPA. These omega-3s have many health benefits, including respiratory advantages.

Note: The lead investigator of the Purdue University study, Laurent Couetil, D.V.M., Ph.D., spoke at the 28th Equine Health and Nutrition Conference, hosted by Kentucky Equine Research. A Q&A that features points from his presentation, titled “Equine Asthma: New Insights in Origin and Management,” is available in the conference proceedings. Read it now! Couetil’s paper begins on page 47.

SHOP KER

^*Couetil, L., K. Ivester, J.R. Burgess, et al. 2025. Fish oil supplementation of Thoroughbred racehorses reduces airway inflammation and improves performance. In. Proceedings of the American Association of Equine Practitioners Convention 71:466-167.

^**Westerfeld, R., F. Payette, V. Dubuc, E. Manguin, K. Picotte, G. Beauchamp, C. Bedard, and M. Leclere. 2023. Effects of soaked hay on lung function and airway inflammation in horses with severe asthma. Journal of Veterinary Internal Medicine16919.

⁺Olave, C.J., K.M. Ivester, L.L. Couetil, J. Burgess, J.H. Park, and A. Mukhopadhyay. 2023. Effects of low-dust forages on dust exposure, airway cytology, and plasma omega-3 concentrations in Thoroughbred racehorses: A randomized clinical trial. Journal of Veterinary Internal Medicine 37:338-348.

⁺⁺Couëtil, L.L., J.M. Cardwell, V. Gerber, J.-P. Léguillette, and E.A. Richard. 2016. Inflammatory airway disease of horses—Revised consensus statement. Journal of Veterinary Internal Medicine 30:503-515.