Over the past two decades feeding a variety of fat and oil sources to horses has become an increasingly commonplace dietary practice.
The role of fat in the horse’s diet has been oversimplified to that as a fuel source. Although this is partly correct that fats can act as fuel molecules, it is equally critical that fats are involved in multiple structural and messaging functions in the body. Therefore, the addition of man-made fats and oils to the equine diet has dramatic implications and consequences to the health of the horse.
The structural unit of fats, fatty acids, are foundational building blocks for cell membranes. Thus, they are important to the health and function of all the cells in the horse’s body. These membranes need to be in top working condition to allow nutrients like glucose into the cell and allow wastes out of the cell. If these membranes are disrupted the cell itself becomes sick. When horses are fed fats that are unnatural and foreign to the horse’s body these “renegade” fats displace and occupy positions in the cell membranes held by normally “healthy” fats. In doing so they disrupt the structural integrity and function of the cell membrane, and ultimately the structural foundation of the horse.
Fatty acids also act as core molecules in the body for hormones and messenger and signal molecules. Once again, if the horse’s natural supply of fatty acids is displaced by man-made fats and oils the quality of communication within the neurological and hormonal networks of the body will be interrupted and disrupted.
Horses have evolved a novel strategy to ensure a constant supply of fatty acids called volatile fatty acids to their body. Volatile fatty acids (VFA) are not found in any feed, rather they are the result of microbial forage fermentation in the hindgut of the horse. The horse absorbs the VFAs into the bloodstream through the cecal and colonic epithelium (gut lining), and they are distributed throughout the body as energy and building blocks for a wide array of biological processes. It is important not to dismiss the important contribution that the VFAs from microbial fermentation make to the health and well-being of the animal.
The fat that horses do need in their diet is highly specific. Their natural diet of primarily fresh and dried forages contains approximately three to five per cent fat. That small percentage of dietary fat contains the two essential fatty acids known as omega-3 and omega-6 fatty acids. These two fatty acids are considered essential to the horse because the horse is unable to produce them with its own enzymes and must acquire these two essential fatty acids from its diet.
Fresh grasses contain appreciably more omega-3 fatty acids than omega-6 fatty acids. Although the exact ratio may fluctuate between 2:1 to 4:1 the proportion of omega-3 fatty acids is invariably higher than the omega-6 portion. Omega-3 and omega-6 fatty acids must be in balance for both to be effective in the horse’s body.
Horses are often fed commercial feeds rich in omega-6 fatty acids but extremely low in omega-3 fatty acids, invariably inverting the optimal ratio. This is because omega-6 fatty acids are overrepresented in the grains and vegetable oils used in processed feeds. The average horse’s diet can have between five and 10 times more omega-6 fatty acids than omega-3 fatty acids.
When “vegetable oil” appears on the ingredient label of a commercial feed it usually refers to soybean oil. Other common sources of oils fed to the horse are corn oil, safflower oil, canola oil, and sunflower oil. All of these oils are rich in omega-6 fatty acids compared to omega-3 fatty acids. Feeding one or more of these oils creates an inverted balance of omega-3s to omega-6s. The skewed ratio of essential fatty acids creates diets which aggravate inflammation in the horse, and are as such inflammatory diets. The method of this has been postulated to occur through the hormonal pathways of inflammation as well as the altercations to the microbial ecology of the gut. Many of these oils are refined and exposed to light, air, heat and solvents during extraction, processing and storage and further challenge the horse to effectively metabolize them.
Flaxseed is often praised as an oil source for horses. What differentiates flaxseed from other fat and/or oil sources is its fatty acid profile. The essential fatty acid ratio of omega-3s to omega-6s in flaxseed is 4:1, similar to fresh grass. Horses that have access to plenty of fresh grass and forage derive little benefit from flaxseed supplementation to the diet. However, as the omega-3 levels in the forage gradually wane over the winter months flaxseed supplementation of one-quarter to one-half cup a day can be a valuable addition to their diet.
Displacing Mother Nature’s preferred form of fatty acids with man-made fats and oils has far-reaching consequences to the health of the horse. The ideal source of balanced fats for horses is found in fresh grasses and forages.