Omega-3 for horses in work: exercise, inflammation and recovery

Every hard session a horse does sets off a minor inflammatory response inside its body. That is normal, and it is part of how the horse recovers and gets fitter. Researchers have measured that response in horses, and then measured what changes when the horses are fed EPA and DHA.

What work does inside a horse

When a horse works hard, its muscles are put under strain and tiny amounts of damage occur in the fibres. The body notices and sends out signals called cytokines, which call in immune cells to clear up and start repair. This is inflammation, the same process that makes a cut warm and swollen for a day or two before it heals.

Liburt and colleagues (2010) measured this directly. Four Standardbred mares ran on a treadmill until they were tired, with blood and small muscle samples taken before, straight after, and over the following 24 hours. Inflammatory signals rose in both the blood and the muscle after exercise, then settled again. The response was real and it was temporary.

Recovery depends on that response doing its job and then closing down. A response that is slow to close leaves the horse stiff, sore and slower to come right for the next session.

Where EPA and DHA come in

EPA and DHA are incorporated into cell membranes, where they influence the signals those cells produce. They also provide the building blocks for specialised molecules, called resolvins, that bring the inflammatory response to a close once its work is done. Exercise creates a normal inflammatory response, and how well the body regulates and resolves that response is part of recovery.

Grass supplies omega-3 as ALA, the short-chain form, and horses turn very little of it into EPA and DHA. The conversion step is covered separately. The studies below fed EPA and DHA directly.

The polo horses

Hess, Braun and Herkelman (2019) worked with 20 conditioned polo horses. Five were fed their normal grain and hay, and three groups of five had DHA added to that diet at different daily amounts for 60 days. Before the study started, and again at 30 and 60 days, every horse did a field exercise test hard enough to set off the inflammatory response, and blood was taken to measure how far the cytokines rose.

In the horses fed the lowest amount of DHA, 10 g a day, the rise in two of those signals after exercise was smaller than in the other groups. The two higher amounts, 20 g and 50 g a day, showed no difference from the control horses.

The Thoroughbreds in training

Wesolowski and colleagues (2022) followed 13 Thoroughbreds in early race training for 12 weeks. Some were fed an oil supplying EPA and DHA, along with GLA, an omega-6 fatty acid, and the rest were fed an oil supplying the short-chain forms, ALA and linoleic acid, instead. At the end of the 12 weeks every horse did a standardised exercise test, with blood taken before it and at 4, 24 and 48 hours afterwards.

The horses fed EPA and DHA had lower levels of IL-8, a signal that recruits inflammatory cells, at 24 hours after the test than the horses fed the short-chain oils.

Heart rate and blood during work

O'Connor and colleagues (2004) fed ten horses either fish oil or corn oil for nine weeks while they were in training, then put them through an exercise test on an incline. During the test the fish oil horses had lower heart rates than the corn oil horses. Their blood cholesterol was lower too.

Stucchi and colleagues (2025) fed six Arabian endurance horses a supplement containing algae extract, plant antioxidants and vitamin C for 21 days, with five horses left on their normal diet. Each horse galloped for an hour before and after the 21 days. Heart rates during the gallop and in recovery did not change, and neither did blood lactate. Creatine kinase, an enzyme that leaks from muscle after hard work, was lower after the gallop in the supplemented horses than it had been before.

What it adds up to

Work sets off an inflammatory response in a horse, and that response has been measured in the blood and in the muscle. In horses fed EPA and DHA, two separate studies in horses in training found the response after a hard test was smaller: the polo horses fed 10 g of DHA a day, and the Thoroughbreds fed EPA and DHA for 12 weeks. Fish oil lowered heart rate during an exercise test in one study, and an algae-based supplement lowered creatine kinase after a gallop in another.

What the equine studies have measured is the inflammatory response to exercise. Whether that translates into horses recovering faster or staying sounder over a season is a separate question, and further research is necessary there.

Feeding EPA and DHA to a horse in work

The training studies ran for 60 days and 12 weeks. What matters in a supplement is which fatty acids it supplies, how much of them the horse gets each day, and how long it is fed for.

Synaxis Core is an algae oil fed at 15 ml a day, giving 3.0 g DHA and 1.3 g EPA. It supplies EPA and DHA straight, without the horse having to make them from ALA, and it is fed as a 90-day protocol to give them time to build up in the body. What happens to EPA and DHA once they are fed is covered in DHA for horses: what actually happens when you feed it.

EPA and DHA belong in a holistic approach to a horse in work, alongside a sensible training programme, appropriate veterinary care, management and nutrition.

To see where your horse's diet stands on omega-3, take the Omega-3 Check.

References

Liburt NR, Adams AA, Betancourt A, Horohov DW, McKeever KH (2010). Exercise-induced increases in inflammatory cytokines in muscle and blood of horses. Equine Veterinary Journal 42(Suppl 38):280-288.

Hess T, Braun S, Herkelman K (2019). The effects of various levels of docosahexaenoic acid on inflammatory markers in conditioned horses during lactate threshold tests. Journal of Equine Veterinary Science 72:64-71.

Wesolowski LT, Simons JL, Pagan JD, White-Springer SH (2022). Impacts of exercise and DHA/EPA/GLA supplementation on plasma cytokines in Thoroughbreds. Comparative Exercise Physiology 18(Suppl 1):S30.

O'Connor CI, Lawrence LM, Lawrence AC, Janicki KM, Warren LK, Hayes S (2004). The effect of dietary fish oil supplementation on exercising horses. Journal of Animal Science 82(10):2978-2984.

Stucchi L, Rossi R, Mainardi E, Ferrucci F (2025). Antioxidant capacity and athletic condition of endurance horses undergoing nutraceutical supplementation. Journal of Equine Veterinary Science 146:105364.