CARBOHYDRATES AND CONFUSION: Sugars and Starches and Energy

This month’s article is the final part- for now- on carbohydrates. We’ll certainly talk about them again in the future, because carbs are such an important part of the horse’s diet. Today we are going to focus on what sugars and starches do and why they are so important to our horses, and how to determine how much your horse is eating…sort of. It’s hard to get an exact number but we’ll talk about the parts that you can figure on your own.

What this article will NOT do is tell you how many units of sugars and starches you should be feeding your horse. That is a discussion to have with your veterinarian. Each horse is an individual and should be fed as such. Your horse’s carb requirement will depend on his age, activity level, overall health, access to forage, breed, environment…so many factors! When you talk with your vet about your horse’s diet, make sure that you understand WHY the vet is making these recommendations. Your vet may mention a feed product by name. Ask him or her why they recommend that product specifically. There is a reason for this: that particular feed may not be readily available in your area, but if you know the specifics, your knowledgeable feed store can help you make a close match. As we’ve discussed before, veterinarians have a lot of information to remember. When you consider the medications and dosages, diseases, anatomies (and so much more) that they must remember, it’s a bit unrealistic to expect them to keep up with the latest feed products too.

A couple points to clarify: usually when people refer to carbs, what they are really concerned about are the sugars and starches. But you will remember from last month’s article that fiber is a carb too and should be the largest part of your horse’s diet. For ease of use, I’m not going to refer to sugars and starches as carbs in this article. I’m going to call them sugars and starches. If I use the word “carb” or “carbohydrates”, then I’m referring to sugars, starches, and fiber.

A quick overview from the last two months: carbohydrates are sugars, starches, and fiber. There are several different ways to categorize carbs depending on their chemical formula, digestibility, and source. Some complex sugars and starches break down into simple sugars in the horse’s small intestine. Other complex sugars, such as fiber, do not break down easily and instead are fermented in the horse’s hindgut. The fermentation provides energy for metabolic processes, including keeping the horse warm. Fiber contains a large amount of indigestible matter, such as lignan, so in addition to producing heat, it also produces a lot of waste. Then you scoop it up and wheel it out to the manure pile.

The sugars and starches that break down in the small intestine are reduced to glucose, which is absorbed into the bloodstream. This triggers a release of insulin which helps move the glucose from the bloodstream to the body tissues. Then the glucose can be metabolized to release energy or stored for future use.

Horses need energy to move their large muscles and for everyday functions such as breathing, maintaining (or gaining) weight, and for powering their brains. It turns out that the horse’s brain is an energy hog. According to the book “Horse Brain, Human Brain” by Janet L. Jones, PhD, the horse’s brain is 0.67 percent of his body weight (about the size of your fist) but uses 25% of his body’s glucose supply. That’s a huge portion.

Obviously, a non-sugar and starch diet isn’t going to work. The horse needs these nutrients. So why are we so concerned about how much the horse eats? It’s because of the impact of too many sugars and starches on his health. And this is a good place to switch to the use of the terms “calories.” When we talk about calories with a small c, we using it as a general term of energy. When we speak of Calories with a large C or kcal, that is a specific measurement and it means the amount of energy needed to raise the temperature of one gram of water by one degree Celsius. It’s like using the terms “shoes” versus “Nike.” One term is general, the other is more specific and tells you exactly what you are dealing with in a quantitative way.

Active horses, such as those who are competing, giving lessons, or doing some sort of work every day, need to have the energy (calories) supplied by sugars and starches. Inactive horses need less. If they eat too many calories, they gain weight and can develop metabolic issues. Horses, like humans, are very good at storing extra calories as fat. This carries him through when food is in short supply, the weather turns cold, or his lifestyle becomes more active but extra food isn’t available. He can burn that stored fat and it releases energy to fuel his body. We’ve all heard stories of owners who are surprised to find that their horses are “ribby” after they shed their winter coat. The most common scenario is that the horse wasn’t getting enough calories to keep him warm, and had to resort to burning his fat stores. (This is another good reason to increase your horse’s hay in winter, as long as he can eat hay. Not only does it provide more calories, it also provides more metabolic heat because the fiber is fermented, not digested. See last month’s article.)

Now I know that many of you have heard, and maybe still believe, that corn will help keep your horse warm in the winter. I’m going to stop you right now before you buy another bag at your feed store. No, corn will not keep your horse warm during cold weather. Hay or forage will do that job. Here is what adding a large amount of corn will do though- increase your risk for colic and laminitis. Not something that you want to deal with! Corn is high in starch. Starch breaks down quickly in the horse’s GI tract, but he can only break down a limited quantity at a time. Too much starch, that is, too much corn, and that starch gets moved through to the hindgut. The purpose of the hindgut is to ferment fiber, so when it gets hit with a payload of starch, it doesn’t have the right microbes to handle the job. The microbes can produce excess gas while trying to ferment the corn, and this can lead to gas colic. Or the microbes may become overwhelmed and die, and by doing so can cause toxins that lead to laminitis.

Ok, you may be thinking, what about adding a small amount of corn? As we said above, corn is high in starch and starch breaks down quickly in horses. You’ll get energy as a result, and it may not be the kind of energy that you want your horse displaying!

So why do we have corn as an ingredient in horse feeds? Corn is a cheap ingredient, and it does have its place. Remember, it provides energy in the form of calories, and it breaks down into simple sugars (such as glucose) that fuel muscles and the brain. Oats are similar in that they are high in sugars and starches too.

Sugars and starches are found in plants. These are energy sources that the grasses have stored for themselves, as plants have nutritional requirements too. The starches are generally stored by the grasses in the seed heads, as any seed that falls to the ground needs to have a source of energy to survive during the winter and then fuel its start as a new plant. When your horse is on pasture, he is getting sugars and starches from the grasses that he eats.

The sugar levels in grasses are very tricky to determine, as they increase and decrease daily depending on the amount of sunshine, the stress level of the plant, and other factors beyond our control. Read the beginning of this paragraph again. That’s right, this large part of our horse’s diet is beyond our control. To a certain extent we can control how much grass our horse eats by limiting pasture, rotational grazing, and paying attention to the time of day that he is allowed to eat grass. But we can’t control the sugars and starches in the grass, and we can’t even get a good measure of the amount, as it is a moving target. If your horse is sensitive to sugars, be aware that frost causes the sugar content to spike in grass. It is nature’s way of trying to provide enough energy to the plant roots to overwinter. Talk with your vet about when you should stop allowing your horse to graze in the fall. It’s also wise to talk with your vet about a practical way to ease your horse into spring-time grazing.

The amount of sugars and starches in hay varies too depending on type of grasses in the hay, the time of day that it was cut, the weather, the time of year, the growing cycle…haying is an art and a science. The hay that is cut on one end of the field can vary from the hay that is cut on the other end. If haying is delayed and the grass has gone to seed, it will have more starch in it. If the grass is stressed due to drought, expect more sugar. How can you tell? Have a hay analysis done. Take handfuls from several bales, bag them up, and take them to your local feed dealer. Many feed companies offer free analysis. Once you have the results, you’ll be able to better determine the amount of carbs (sugars, starches, and fiber) that your horse is eating. If you find that your hay is high in sugars and starches and your horse is sensitive to them, your vet may recommend soaking your hay. Typically soaking for 30-60 minutes will reduce the amount of sugars in the hay. If you do it longer than that, it is possible that some of the other nutrients will leach out as well. (There aren’t a lot of studies on this yet.) It’s important to note that soaking the hay doesn’t mean that your hay will now be in a safe range, it just means that you are lowering the sugar content. Recent studies show that soaking is more effective in lowering sugar than steaming.

I know that it is a nuisance to soak hay in the winter here in northern New England, and I wish I had a simple way to suggest to you. Some people put it in hay nets and soak it in clean manure tubs or clean wheelbarrows. Some people do it in their cellar and then drain it outside. I’m afraid you’ll just have to experiment and see what works best for you and your stable set-up. Another option, although an expensive one, is to switch your horse to chopped forages that come in a bag. This is hay that is nutritionally consistent. There are many options available, and they vary in the types of grasses and the nutritional content. They may make sense for you if you are feeding a mini (who can be very sugar sensitive) but maybe not if you are feeding draft horses. Of course, any changes that you make in the forages that you feed should be done over a period of time, at least two weeks, to allow your horse’s microbes to adjust.

Let’s look at how we determine your horse’s daily intake of sugars and starches. When people talk about a low-carb diet, what they usually mean is a low sugar and starch diet. You certainly don’t want a low fiber diet for the reasons we’ve discussed before. Even if your horse can’t eat long-stem hay or can’t chew grass, he needs fiber in his diet, and it most likely will have to come from a source such as beet pulp. This is what remains after the sugar has been extracted from sugar beets and has very little sugar left in it.

Sugars and starches are frequently referred to collectively as non-structural carbohydrates, or NSCs. Luckily for us, many of the mid-range (fixed formula) feeds and most of the top-line (fixed nutrition) feeds will give you info on NSCs in their guaranteed analysis. Low cost/least cost ingredient feeds won’t because they can’t guarantee the amounts. You may have to do a bit of work though to figure it out. The bag tags will likely list sugars and starches (also listed as dietary starch) separately. Just add them together to find out the total percentage. And remember, this is the percentage of sugars and starches that are in the bag. Be aware that there generally is a range of a couple percentage points. The numbers on the bag are averaged across many batches of feed and many nutritional analyses.

Another important number that you may see in the guaranteed analysis is digestible energy. This means the number of Calories per pound in the feed, and it is expressed as kcals/lb in American feeds and mcals/kg in European feeds (yes, you will have to do a conversion.) Some feeds won’t list digestible energy. The feed companies will tell you that it is because there are different ways to measure it and it can be hard to compare the figures from one company with those from another company. And that brings up a good point. There are still some black holes in animal nutrition, and one of these is having a fail-safe way to evenly compare products from different companies.

One prime example is the use of the term “low NSC.” There are different ways to compute the NSC value, and there isn’t a numerical value for what low NSC means. Case in point: there is one very popular feed that claims it is low starch and sugar, and its calculated value is 19% NSCs. Another company claims that its senior feed has a low level of NSCs, and its calculated value is 11%. Obviously we can see that 11% is lower than 19%, but does that mean that 19% isn’t low? Should 19% be considered mid-range? What if I told you that corn and oats may have an NSC range of 40% to 60%? How does that change your perception? Don’t rely just on the advertising; do the math.

To make things even more complicated, NSCs are determined by calculating starch and WSCs, or water-soluble carbs. You may see ESCs, or ethanol soluble carbs, and sometimes this is used in the calculation of NSCs. The difference is the types of sugars and how much glucose they contribute to the horse’s blood level, and the results matter because they can affect the horse in different ways metabolically. There are still many studies being done on this, and equine nutritionists argue as to whether it is better to consider the combination of ESCs and starch or WSCs and starch in a horse’s diet. There are pros and cons to both sides.

Suppose your vet says that your horse needs to be on a diet that is no more than 12% NSCs. How do you calculate how much your horse is eating daily? It’s nearly impossible to calculate the NSCs in grass as discussed above, but you can calculate his feed and hay. You will need to know how many pounds he eats of each. Note that we’re talking pounds, not scoops, and it really does matter in your calculations. Let’s say that, according to the feed bag, the dietary starch and sugars add up to 20%. That means that 20% of the 50-pound bag, or 10 pounds, consists of sugars and starches (.20 x 50 = 10). Your horse eats two meals of two pounds each for a total of four pounds per day. Doing the math gets you an answer of 0.8 pounds per day of sugars and starches that he gets from his feed (.20 x 4 = 0.8). Now do the same for his hay. If he eats 20 pounds per day and your hay analysis shows that the NSC level is 15%, then he is getting three pounds per day of starches and sugars from his hay (.15 x 20 = 3). Remember that you must calculate this using the weight of the hay in pounds, not in flakes. Flakes differ depending on the baler settings and the density of the cutting.

Last step: you are ready to calculate the percentage of NSCs by adding the total pounds of sugars and starches, and dividing that by the total pounds of feed and hay. In our example above, 3.8 pounds of sugars and starches divided by 24 pounds of feed and hay yields 15.8%. Time to talk with your vet and feed store about other feed options! Remember too that if you feed additional items like timothy pellets or beet pulp, you’ll need to figure those into your calculations also.

Ration balancers are in the lower end of the NSC spectrum with most between 10% and 15%. This makes sense when you think about their purpose: they are supplements that provide protein, vitamins, and minerals. Given their low feeding rate of one to two pounds per day, they are not a significant source of sugars.

Lastly, what about treats? Apples, carrots, and most commercial treats are high in sugars. There are treats on the market that are low sugar/low NSC and are very palatable to horses. Still, if you are a treat-feeder, please do so in moderation for the sake of your horse’s health. Peppermints can cause a sugar spike in your metabolic horse’s bloodstream.

Sugars and starches can be confusing. We know that our horses need them, but it can be tricky to determine how much they need and how much they are eating. Don’t rely on advertising to make your feed choices when it comes to determining the best diet for your horse. Ask your veterinarian and talk with someone who is knowledgeable at your local feed store. Then be prepared to do some math and research to make your best decision. Whether your horse needs fewer sugar and starches or more, there is a diet out there that will fit him and there are people who can help you find it.