Added Fat Improves Behavior

By Juliet M. Getty, Ph.D.

Diet affects behavior. This makes sense. A well fed horse is healthy. And a healthy horse feels good. Conversely, a poorly-nourished horse is suffering. A variation in hormone levels, for example, can have a temporary effect on how your horse sees the world. Think about how yourself - if you overindulge in high amounts of sugar, for example, you may have a burst of energy, followed by a need to take a nap. Or you may feel ill to your stomach. Excessive sugar can make horses nauseous, as well.  And they certainly have been known to exhibit "sugar highs and lows" caused by a sudden surge in blood glucose after a high sugar/high starch meal, only to slow down once all that excess sugar is tucked away for storage or turned into fat. But it's important to note that not every horse responds the same way to high carbohydrate diets (sugar and starch). In fact, there is little scientific evidence that proves this. Nevertheless, many horse owners will attest to their own horses having adverse behavioral responses and will therefore, avoid feeding anything that contains starchy cereal grains or is sweetened with molasses.

There are plenty of good reasons to avoid high sugar/high starch diets that are beyond the scope of this article. But in terms of behavior, what alternative does a horse owner have if the horse simply needs more calories? Hay and grass simply cannot provide enough energy (calories) to support the additional requirements created by exercise, work, and performing. The answer is fat.

Gram for gram, fat provides more than double the calories than what carbohydrates (or protein) can offer. And it is well digested. But there's an added bonus! Fat has a calming effect on horses' behavior.

Researchers at Virginia Polytechnic Institute[i] noticed that horses fed a high fat diet are less reactive to startling stimuli and had lower levels of excitability and anxiety than horses fed a more traditional grain-based diet. The horses in their experiment received 15% of the total calories from fat, which is high for most horses. However, it reveals that fat is worth trying if you have a sensitive horse who may become easily excited by every day activities. (Please note: Ponies, minis, donkeys, and mules should not receive high fat diets.)

What type of fat?

All fat has the same number of calories, regardless of the source. But from a health perspective, it is best to steer clear of animal fats, as well as oils that are have too many omega 6s (which increase inflammation) in relation to omega 3s (which have an anti-inflammatory effect). Oils high in monounsaturated fatty acids are a good source since they neither increase nor decrease inflammation. Below are some commonly fed oils:



Flaxseed oil

4:1 Omega 3s to Omega 6s (ideal choice)

Soybean oil

Only 7% omega 3s and mostly omega 6s

Corn oil

No omega 3s and higher in omega 6s than soybean oil (poorest choice)

Canola oil

10% omega 3s and relatively low in omega 6s. Also contains monounsaturated fatty acids (no harmful impact on inflammation)

Soy lecithin

4% omega 3s but also contains choline, a component of neurotransmitters

Rice bran oil

Only 1% omega 3s but low in omega 6s and high in monounsaturated fatty acids


How much?

I prefer to limit fat intake to no more than 10% of the total calories, though some athletes are fed levels as high as 20%. For the lightly exercised, mature 1100 lb (500 kg) horse, the National Research Council recommends a minimum of 20 Mcals per day to maintain body condition. Ten percent would be 2 Mcals per day from fat. One cup (8 fluid ounces or 240 ml) of oil will meet this requirement. It weighs 240 grams and at 9 kcals/g, provides 2.16 Mcals. When adding any amount of oil to your horse's feed, start with a small amount (say, one tablespoon or 15 ml). Most horses do not like oily feed, but more importantly, it takes several weeks for the horse's cells to become accustomed to metabolizing more fat.


Short attention span, spookiness, reluctance to work, excessive sensitivity and alertness to surroundings, irritability, and "hot" behaviors can be reduced by adding fat to the diet. Fat is high in calories, so limit the amount you feed based on the horse's weight and his caloric need. Omega 3s need to be in balance with omega 6s, so choose oils carefully. And finally, build up to desired intake by starting slowly and increasing over 4 to 6 weeks.


[i] Holland, J.L., Kronsfeld, D.S., and Meacham, T.N. 1996. Behavior of horses is affected by soy lecithin and corn oil in the diet. J. Animal Sci. vol.74, no 6, 1252-1255.


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