For years we all have been told to feed oil such as corn, canola or vegetable oil which is usually soy to our horses for many different reasons. The intention is good but the oil is the wrong type of oil. Do not feed your horses corn, soy, canola, or any other inexpensive grocery store oils.
These oils are unhealthful for your horses and for humans as well. The reason being they are high in what is called Omega 6 fatty acids. You may hear this promoted as being something desirable but this is not the type of fatty acids that provide health benefits.
Omega 6 is pro-inflammatory. What this means is if your horse has arthritis or other inflammatory conditions these oils will make the condition worse.
High fat in a horses diet can be beneficial if it is the right type: high in Omega 3's and Omega 9's, low in Omega 6. Omega 3 fatty acids are anti-inflammatory.
Because of this, they will help a horse with joint with issues.
Fish oil is what is normally recommended for human consumption to obtain a good quality fatty acid supplement. For your horse there are other types of vegetable oils that are good quality to supplement the diet with.
Flax oil, coconut oil, rice bran oil, and hemp seed oil are good options. With that said, not all of these oils are created equal. What makes a big difference in the quality of the oil is the way it is processed.
For example; there are several different brands of rice bran oil that are manufactured and promoted for horses. If you pay attention to the ingredients most of them are not 100% rice bran oil. They are usually mixed with soy oil because it is less expensive to manufacturer and it will be promoted as rice bran oil. The inexpensive types will be light in color, thin and have no sediment in it. These will not provide the same health benefits to your horse.
Rice bran oil should be dark in color and contain thick lecithins which are high in Vitamin E and other health giving properties. The best rice bran oil is McCauley's
Once you have used this oil you will see a huge difference in the quality of the oil and the results with your horse.
Flaxseed oil is also darker in color and should not be mixed with other inexpensive oils. A good quality flaxseed oil is from Platinum Performance called Healthy Weight.
Coconut oil is harder to feed because in cooler weather it hardens. A good form of coconut oil is a product called Power Stance
Hemp seed oil is a wonderful oil for horses. It provides a good ratio of omega fatty acids. Organic hemp oil for human consumption is an excellent choice.
Oils go rancid fast so they must be kept in a cool/dark area and out of direct sunlight. If you live in a humid climate best to keep them refrigerated. Too often I see bottles of canola or soy oil sitting out in the sunlight in front of a horses stall or paddock. This oil when heated by the sun becomes toxic to your horse creating inflammation in the body.
Choose your oils wisely and learn to read the ingredient labels. The label on the front may say Rice Bran Oil but if you read the little side label of the actual ingredients you will find other oils mixed with it.