Vegetable oil is generally safe for horses and can be a useful addition to their diet when fed in reasonable amounts. It provides a concentrated energy source, delivering roughly 2.25 times more calories than the same weight of digested carbohydrates. That makes it a practical option for hard keepers, performance horses, or any horse that needs extra calories without more grain. However, not all vegetable oils are equally beneficial, and the type you choose matters more than most horse owners realize.
Why Oil Works as a Horse Feed
Horses don’t have a gallbladder, but they still digest fat effectively in the small intestine. Under ideal conditions, fat digestibility in horses approaches nearly 100%. In practice, studies measuring absorption before the cecum found that horses digested between 73% and 86% of added fat when fed at a rate of about 1 gram per kilogram of body weight. Some undigested fatty acids do reach the hindgut, but this doesn’t appear to cause problems at moderate feeding levels.
The caloric density is the main appeal. Half a scoop of oil contains roughly the same energy as a full scoop of grain concentrate. For a horse that’s losing weight on hay and grain alone, or one that gets too hot on high-starch feeds, oil lets you add calories without increasing meal volume or sugar intake.
Which Horses Benefit Most
Horses with conditions like Polysaccharide Storage Myopathy (PSSM) or Equine Metabolic Syndrome need diets low in starch and sugar. For these horses, replacing grain calories with fat calories is a core management strategy. If a horse with PSSM needs more energy than forage alone provides, adding oil to the diet is one of the safest ways to fill that gap.
Performance horses also benefit. Fat is a slow-burning fuel source compared to starch, and horses adapted to higher-fat diets can use it more efficiently during sustained work. Endurance horses in particular are commonly fed supplemental oil. Hard keepers, older horses struggling to maintain condition, and horses recovering from illness are other common candidates.
Not All Vegetable Oils Are Equal
This is where the choice gets important. Common vegetable oils like corn oil and soybean oil are high in omega-6 fatty acids relative to omega-3s. That ratio matters because omega-6 fatty acids promote inflammatory pathways in the body, while omega-3s help counteract inflammation.
A study at Texas A&M University found that horses fed diets higher in omega-6 fatty acids had elevated fibrinogen levels, a marker of inflammation, compared to horses on diets with more balanced or omega-3-rich fat sources. The horses on higher omega-6 diets also showed increased concentrations of linoleic acid (the primary omega-6 in most vegetable oils) in their blood. This suggests that while corn oil and similar options do provide calories effectively, they may nudge the horse’s body toward a more inflammatory state over time.
Canola oil offers a somewhat better omega-6 to omega-3 ratio than corn or soybean oil, making it a middle-ground option. Flaxseed oil is the strongest choice if reducing inflammation is a priority, as it’s naturally rich in omega-3 fatty acids. For a horse with joint issues, skin problems, or any condition where inflammation plays a role, flaxseed or canola oil is a better pick than corn oil.
How Much Oil to Feed
Horses can handle added fat making up to 15% of their total diet without negative effects on fiber or protein digestion. At that level, no adverse side effects have been reported in research. Most horse owners feed well below that ceiling. A common starting range is a quarter cup per day, gradually increasing over a couple of weeks to the target amount.
For a 1,100-pound horse, many owners settle somewhere between half a cup and two cups daily, depending on the horse’s caloric needs. The key is a slow introduction. Jumping straight to a full dose can cause loose stool or digestive upset. Increase by about a quarter cup every few days, giving the horse’s digestive system time to ramp up fat-processing capacity. If your horse is prone to colic or has a sensitive gut, stretch the transition period out even longer.
Practical Tips for Adding Oil
Most horses accept oil readily when it’s mixed into their grain. Some are pickier. Starting with a small amount helps the horse get used to the taste and texture. Corn oil tends to be the most palatable to horses, which is one reason it became popular despite its less-than-ideal fatty acid profile. Canola oil is generally well accepted too. Flaxseed oil has a stronger flavor that some horses resist initially but usually tolerate once introduced gradually.
Store oil in a cool, dark place and check for rancidity before feeding. Rancid oil smells off and can irritate the digestive tract. In hot climates or during summer months, oil goes bad faster, so buying smaller containers and using them within a few weeks is a practical approach. If you’re top-dressing oil onto feed, mix it in well rather than pouring it on top, as some horses will sort around a pool of oil sitting on their grain.
One thing oil won’t provide is vitamins or minerals. It’s pure energy. If you’re replacing a portion of a fortified commercial feed with oil, you may need to adjust the rest of the diet to avoid shortfalls in micronutrients. Adding a ration balancer alongside oil and forage is a common solution for horses that don’t need much grain but do need supplemental calories.
The Bottom Line on Oil Type
Vegetable oil is a safe, effective calorie source for horses. The real question isn’t whether to feed oil, but which one. Corn oil works and horses like it, but it’s heavy on omega-6 fatty acids that can promote inflammation. Soybean oil falls into a similar category. Canola oil is a better balanced, affordable everyday option. Flaxseed oil is the premium choice for horses where inflammation, coat quality, or joint health is a concern. Whichever you choose, introduce it slowly, keep it fresh, and stay within the 15% total dietary fat ceiling to keep your horse’s digestion running smoothly.