By Kristen M. Janicki
Fats serve many important functions for your horse, from increasing calorie consumption to reducing gastric ulcer severity
Society has seen its share of diet crazes, even in the past decade. From low-carb and high-protein to low-fat and high-fiber, trends have come and gone and come again, making food selection challenging. Luckily, horse owners don’t have as many options when they’re picking their charges’ feed. As herbivores, our horses’ diets must be high-fiber complemented by a commercial product fit to meet their life stage (performance, breeding, growing, etc.). The high-fat diet era began as a way to effectively increase calories without drastically increasing feed volume and, as researchers learn more about the benefit of fats for our four-legged friends, it appears that high-fat diets are here to stay.
What Exactly are Fats?
Fats and oils are part of a class of molecules called lipids. Structurally, all fats contain the following components:
- A single glycerol molecule A chain of three carbon atoms, each with a hydroxyl group (oxygen and hydrogen) bound to it; and
- Fatty acids Long hydrocarbon (containing, you guessed it: hydrogen and carbon) chains.
The fatty acids attached to glycerol vary in length and in how their own carbon molecules are linked. When single bonds link carbon atoms, the fatty acid is considered saturated. Saturated fat originates predominantly from animal fat sources such as tallow. Conversely, when one or more double bonds link the carbon atoms, the fat is unsaturated. Horse diets consist mainly of unsaturated fats such as vegetable oils.
Fats can be found in forages and grains in many forms, including di- and triglycerides, sterols, and phospholipids. The fats we typically supplement as oil are predominantly triglycerides. Each fat type varies significantly in its availability to the horse, which we will discuss later.
Digestion and Absorption
Once a horse ingests fat, enzymes (called lipases) in the stomach begin to break it down. A majority of fat digestion takes place in the small intestine, specifically in the duodenum and jejunum. After absorption, fats move along to the liver, adipose tissue, or elsewhere as needed for storage or use. Fats that do not get absorbed in the small intestine travel to the hindgut (the large intestine and colon), where they will be excreted in the feces.
In several studies researchers have found drastic differences in the digestibility of various fat sources in the horse’s diet. Fats from forages appear to be 55% digestible, whereas fats from oil are 100% digestible. This makes sense, considering that cell wall components more than likely surround the fats in forages and make them less available for digestion.
Chew the Fat
Researchers have compared the palatability of both animal and plant-based fat sources to horses and found corn oil to be the most acceptable, but other sources can be just as readily consumed. See common sources of fat used in equine diets in the table below:
|Source||Avg. Fat (%)||Points to Consider|
- Highly palatable source of calories
- Serves also as a quality source of amino acids
- Contains trypsin inhibitors and must be heat-processed prior to feeding
- High in omega-3 fatty acids
- Due to hard outer coat, should be ground prior to feeding
- Good source of fiber and contains gamma oryzanol, an antioxidant that might improve muscle quality
- Inverted calcium to phosphorus ration
- Contains a naturally occuring enzyme (lipase) that increases rancidity if not stabilized
- High in potassium and omega-6 fatty acids
- High in omega-3 fatty acids
- Odor can be a deterrent to horses and owners
Why Horses Need Them
“It is important to understand that there are two types of fats: dietary fats and polyunsaturated fatty acids,” says Stewart K. Morgan, DVM, PhD, clinical nutrition resident at the Virginia-Maryland College of Veterinary Medicine, in Blacksburg. Dietary fats, also known as the triglycerides mentioned earlier, are a concentrated source of dietary energy that provides essential fatty acids (EFAs) and can carry the fat-soluble vitamins A, D, E, and K. Because hydrogen and carbon atoms make up these vitamins’ structure, they are hydrophobic in nature. Have you heard the saying “oil and water don’t mix”? Hydrophobic literally means “water-fearing” and describes oil’s propensity to separate from water. Therefore, fat-soluble vitamins need fats to help transport them across the small intestine. Extremely low-fat diets can potentially reduce fat-soluble vitamin absorption, as seen with decreased vitamin E levels in ponies fed an extremely low-fat diet.
Meanwhile, polyunsaturated fatty acids can be metabolized to form compounds that serve biological functions. “These include omega-6 and omega-3 fatty acids, which are essential to the horse,” says Morgan.
Horses cannot synthesize EFA on their own and rely on dietary sources to meet their needs. The two most biologically relevant EFAs, a-linolenic acid (omega-3) and linoleic acid (omega-6), play a vital role in the immune system, central nervous system, and cell membrane structure, to name a few. The average equine diet tends toward greater omega-3 intakes than omega-6.
In a two-year study conducted at the University of Florida, researchers found that the fat content in bahiagrass (a warm-season pasture grass species) contains 40-55% omega-3 fatty acids and as hay contains 18-35%. Although hay and pasture are low in total fat content, typically offering less than 5%, most of the fat is made up of omega-3 fatty acids, whereas the fat in cereal grains, like what you’d find in horse feed, is made up primarily of omega-6 fatty acids.
Morgan says researchers are still trying to determine horses’ EFA requirements, but there is some evidence that horses might benefit from fatty acid supplementation in certain conditions. Currently, Nutrient Requirements for Horses (2007) suggests horses receive a minimum of 0.5% of dry matter in linoleic acid, equivalent to approximately 50 grams per day for the 1,100-pound horse. Nutritionists have yet to set an exact requirement for a-linolenic acid, but horses more than likely consume adequate levels with good-quality forage.
What Do They Do?
Fats can benefit many aspects of a horse’s health. “Although a typical forage-based equine ration should meet a horse’s EFA requirements, there are benefits to supplementation under certain conditions, such as meeting a medical need to gain weight, managing inflammatory conditions like heaves and arthritis, or preventing and managing gastric ulcers,” Morgan adds. Owners of performance horses, especially those requiring a large amount of digestible energy to support high-intensity performance, feed fats to increase a meal’s caloric density without also increasing its volume. Let’s take a look at the unique benefits of fat unveiled by recent research:
Calories Pound for pound, fat contains 2¼ times more energy than do carbohydrates. Horses use fat for energy production without needing a drastic increase in feed volume. Broodmares and performance horses, as well as horses below ideal body condition, benefit from fat in their diets.
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