Walking down the aisle of a grocery store, chances are you will find an “excellent source of omega-3” on product labels from eggs to dog food. While consumers have some idea of the health benefits of essential fatty acids, they may not have an idea of the health implications for themselves and their animals.
Arguably, the most important omega-3 fatty acids are docohexaenoic acid and eicosapentaenoic acid. These are found primarily in marine sources like fish and algae.
While the typical equine diet is low in crude fat, fatty acid supplements for horses have been promoted for improving skin, coat and hoof quality.
The exact daily requirements for horses remain unknown because of the novelty of omega-3 research in horses.
However, docohexaenoic acid and eicosapentaenoic acid are absorbed and incorporated into tissues in horses, and recent research suggests this may have an important role in equine health and nutrition beyond skin and coat.
Docohexaenoic acid has a role in reproduction from breeding and conception to foal development. Stallion semen contains high levels of docohexaenoic acid and eicosapentaenoic acid, and in studies with boars, a higher ratio of docohexaenoic acid to DPA (an omega-6 fatty acid) enhances fertility.
Like boars, stallions produce sperm that respond poorly to cooling or freezing, making transportation for A.I. a challenge.
Cooling or freezing semen reduces motility, but this can be partially alleviated when stallions are fed a high-docohexaenoic acid supplement.
Semen lipid profiles have a major role in the tolerance of sperm to cold shock and freezing, and while there is limited information in horses, docohexaenoic acid content is directly correlated to motility and viability after freezing in other mammals.
In the mare, docohexaenoic acid can help with post-breeding uterine inflammation. Mares given an algal docohexaenoic acid supplement had less inflammation post-breeding with frozen semen.
Following breeding, docohexaenoic acid becomes important for the proper development and function of the foals’ brains. In fact, in humans’ maternal milk, docohexaenoic acid content is related to cognitive performance in children.
The importance of docohexaenoic acid on neonatal development has been widely noted – but again, studies are limited in horses.
It is known that docohexaenoic acid transfers to the foal when mares are fed even small amounts of docohexaenoic acid and that this increase in turn leads to improvements in foal behaviors like time to nurse and stand.
As the animal ages, docohexaenoic acid takes on other roles physiologically. Fat is added to diets to meet the increasing energy requirements of exercising horses.
However, there could be additional benefits to adding fat in the form of omega-3 fatty acids, particularly docohexaenoic acid.
In horses and other species, adding marine-source docohexaenoic acid to the diet can reduce oxygen consumption and heart rate during exercise.
Docohexaenoic acid and eicosapentaenoic acid supplementation increases the number of mitochondria, the organelle responsible for adenosine triphosphate production for energy, in skeletal muscle – suggesting docohexaenoic acid could help improve exercise capacity.
As a horse matures, insulin resistance and metabolic issues become more common. Insulin resistance is a broad term that is used when a normal concentration of insulin does not produce a normal biological response (i.e., uptake of circulating glucose).
Insulin resistance and the associated elevation in insulin levels (called hyperinsulinemia) are two of the main components in equine metabolic syndrome and can predispose horses to laminitis.
While increasing exercise and decreasing caloric intake are commonly recommended to treat insulin resistance, these management practices are not always successful.
In addition, pharmaceuticals have resulted in conflicting results from scientific studies as to the efficacy and safety of the products.
While high-fat diets can lead to impaired insulin signaling, multiple studies have shown that diets rich in omega-3 fatty acids improve insulin sensitivity in rodent models of insulin resistance, suggesting that fatty acid form has a profound effect on insulin metabolism.
Ideally, a nutritional solution for the management of insulin resistance could provide a way for safe, long-term management of insulin-resistant horses.
Researchers found that omega-3 supplementation, especially from a marine source, led to increased docohexaenoic acid and eicosapentaenoic acid skeletal muscle content but had no effect on basal glucose and insulin and only tended to improve insulin sensitivity in horses classified as insulin-resistant.
However, recent work found that daily supplementation with a docohexaenoic acid-rich algae increased insulin sensitivity and estimates of pancreatic β-cell responsiveness in insulin-resistant horses.
Overall, our understanding of the role of docohexaenoic acid in horses from birth to the aging horse is just beginning. While the actual docohexaenoic acid requirement in the equine diet is unknown, research has proven that docohexaenoic acid is essential for optimal health and performance of horses in all life stages.
References omitted due to space but are available upon request.
Kristen M. Brennan
Research Project Manager
Equine Nutrition and Animal Nutrigenomics