Guest Post by Karen Briggs: The Oily Truth

Writing From the Right Side of the Stall
Author of Understanding Equine Nutrition
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Work: day off.

Backstory: Previous Horse and the mare had their feed top dressed with vegetable oil for years. They were so shiny that dirt just rolled off. When Rodney showed up, on he went. Then Greg read a paper saying that corn oil made horses less nervous. We switched Rodney & the mare over. Big mistake. On corn oil, Rodney had his worst day ever. Once I realized that it might stem from his diet rather than my horrible horse handling, we dropped all oil. Unfortunately, this lead to dry fur and static shocks. We compromised with flaxseed oil. After Rodney seemed to do well, we switched the mare over figuring that if corn/vegetable oil is hard to digest on a sensitive stomach, perhaps it is hard for an older horse to digest. On the flax/rice, her weight picked back up, her coat brightened, and she stopped looking quite so geriatric. Apparently, we inadvertently stumbled unto a hot topic in horse nutrition. Equine writer and equine nutrition expert Karen Briggs has agreed to explain more fully. Welcome Karen:

In nutrition textbooks, where we can isolate the variables and monitor down to the nanogram the ingredients we’re feeding, horses tend to react in predictable and similar ways to changes in their diet.

In the real world, not so much.

Although you can make lots of generalities in nutrition, there will always be one horse who was put on this earth to make you look like an idiot. It’s important to remember that each horse is an individual, that there’s an exception to every rule, and that feeding is nine parts science to one part witchcraft (or at least, the willingness to try something else).

So…. fat. We’ve known for a few decades now that, despite horses have virtually no sources of fat in their natural (ie. ‘wild’) diets, they digest it well and can use it as an aerobic energy source. There are a few advantages to this:

a) fat contributes almost 2 ½ times as much energy, ounce for ounce, as carbohydrates, so it can serve as a concentrated energy source to replace a portion of the grain in a high-performance horse’s diet

b) Carbs (grain) can only be processed at a certain rate in the small intestine; anything that doesn’t get digested there, gets fermented in the hindgut instead, leading to cecal acidosis, and possibly colic and/or founder. Fat, on the other hand, is easily digested, doesn’t trigger cecal acidosis, and also doesn’t cause major fluctuations in insulin levels.

c) horses who aren’t working hard tend to do the same thing we do with fat – turn it into body fat. So it’s great for putting weight on a hard keeper or a geriatric.

d) Studies have shown that horses fed a fat-supplemented diet are “less reactive” (ie. calmer and less spooky) than horses on a hay and grain diet with no added fat.

e) A nice byproduct of feeding fat is a shiny coat and flexible, less brittle hooves.

Among the ‘traditional’ ways of adding fat to the diet is top-dressing corn oil. Before we understood the benefits of fat as an energy source for horses, we top-dressed it merely to improve the coat, and horses always seemed to do well on it. Corn oil was long preferred over other types of vegetable oils because it’s very palatable to horses – unlike some other sources, like canola oil, which most horses think tastes a bit funky.

Closer inspection, however, has recently revealed that corn oil has a rather unsavoury proportion of omega-6 fatty acids as compared to omega-3. Omega-sixes are fatty acids which are considered ‘inflammatory’; that is, they can aggravate inflammation on a cellular level throughout the body. Omega-threes, in contrast, are thought to help control inflammation on a cellular level.

Some other vegetable oils, such as soy oil and flaxseed oil, as well as rice bran (which is about 20% fat and is often top-dressed as a fat supplement) have better ratios of omega-3 to omega-6 than corn oil, and are gaining in popularity for top-dressing, even though they aren’t as yummy. (The very best source of omega-threes, by the way, is fish oil, but good luck getting most horses to eat that.)

So did hyper-sensitive Rodney react to the omega-sixes in his corn oil? It’s certainly possible, and there are plenty of anecdotal accounts about, of horses responding similarly.

Does every horse react like that to corn oil? Nope, or it wouldn’t have been such a popular feed additive for the last umpteen decades.

Can we pin Rodney’s behaviour definitively on the corn oil and only the corn oil? Nope, because in the real world it’s really hard to isolate the variables, and Rodney, as we know, has issues about a lot of stuff, not all of which are physical in origin.

We also don’t yet understand what the ideal ‘dose’ of omega-threes might be, and the truth is it is probably going to be different for every horse, depending on how much in the way of inflammatory processes is already going on in his body.

But if Rodney is more agreeable on another fat source, and if that fat source is also delivering benefits for his geriatric companion, then it’s definitely the right call.

Have you had a horse who reacted badly to the addition to corn oil in his diet? Have you tried other fat sources and noticed a difference?