Omega-3 for metabolic horses: grazing, hay and DHA

A horse out on good grass takes in omega-3 all day long, because fresh, growing grass is where horses have always got it. Metabolic horses are often the ones kept away from that grass.

What "metabolic" means

Most metabolic horses have equine metabolic syndrome (EMS), and its central feature is insulin dysregulation. When these horses eat sugar or starch, their bodies release more insulin than normal and it stays high for longer. They tend to be good doers that gain weight easily, often carrying fat on the crest of the neck and around the tailhead. Persistently high insulin can trigger laminitis, so management centres on controlling the sugar and starch that drive the insulin response. Grass is often the largest source of both, which is why grazing is restricted with muzzles, track systems, dry lots and limited turnout.

Where the omega-3 goes

Fresh grass contains alpha-linolenic acid (ALA), a plant omega-3, and much of it is lost when grass is cut and dried into hay (what happens to omega-3 when grass becomes hay). The horse most likely to have its grazing deliberately restricted is therefore also the horse most likely to lose its main source of omega-3.

Grass supplies ALA rather than EPA and DHA, the omega-3s the body builds into its cells. Horses convert only a small amount of ALA into EPA and DHA (the conversion step horses depend on), so feeding EPA and DHA directly gives the horse the form its cells use.

What the equine studies show

Two studies from the University of Kentucky fed DHA-rich microalgae to horses. The first created insulin resistance in healthy horses using a drug, and the second studied horses diagnosed with EMS.

Brennan and colleagues (2015) fed eight healthy horses a DHA-rich microalgae meal at 150 g a day or a control diet, then switched them over. In each period the horses were given dexamethasone, a steroid that reduces the body's response to insulin. After the dexamethasone, the horses had lower resting insulin and glucose levels on the microalgae diet than on the control diet.

Elzinga and colleagues (2019) studied ten horses with EMS kept in dry lots on hay. Six were fed a DHA-rich microalgae supplying 16 g of DHA a day for 46 days, and four were controls. At the start, the two groups responded to an oral sugar test with similar rises in insulin. By day 46, the control horses' insulin response had increased and was significantly higher than that of the fed horses, whose response stayed level. The fed horses' blood DHA rose, and their serum triglycerides fell and were significantly lower than the controls' by the end of the study.

Both studies used DHA from algae, the same source as Synaxis Core. Further research in larger groups of metabolic horses is necessary.

What EPA and DHA do in the body

EPA and DHA are built into cell membranes, where they influence the signals those cells produce. They also provide the building blocks for specialised molecules that bring inflammation to a close. Feeding them directly skips the conversion from ALA.

Where omega-3 fits in metabolic management

Managing a metabolic horse starts with body condition, grazing, the sugar and starch in forage and feed, and exercise where the horse can do it. Omega-3 sits alongside that management and answers a separate question: once fresh grass has been taken out of the diet, what replaces the fatty acids it supplied?

Feeding Synaxis Core to a metabolic horse

Synaxis Core is an algae oil fed at 15ml a day. It contains no sugar or starch, so it fits a restricted, forage-based diet, and it provides DHA and EPA directly. It suits horses whose access to fresh grass is restricted.

The studies above measured changes over several weeks, and Synaxis Core is fed as a 90-day protocol.

References

Brennan KM, Graugnard DE, Spry ML, Brewster-Barnes T, Smith AC, Schaeffer RE, Urschel KL (2015). Effects of a docosahexaenoic acid-rich microalgae nutritional product on insulin sensitivity after prolonged dexamethasone treatment in healthy mature horses. American Journal of Veterinary Research 76(10):889-896. doi:10.2460/ajvr.76.10.889

Elzinga SE, Betancourt A, Stewart JC, Altman MH, Barker VD, Muholland M, Bailey S, Brennan KM, Adams AA (2019). Effects of docosahexaenoic acid-rich microalgae supplementation on metabolic and inflammatory parameters in horses with equine metabolic syndrome. Journal of Equine Veterinary Science 83:102811. doi:10.1016/j.jevs.2019.102811