Horse Feed Fillers

Let’s talk fillers.

Many people are concerned with the idea of fillers in horse feed. Similar to other trends in equine nutrition, this concern is largely due to a crossover from human nutrition. However, it’s important to consider the differences in human and horse digestive tracts and why this matters so much specifically to the concept of fillers.

In the human nutrition world, fillers are generally defined as ingredients that provide bulk without offering any nutrition. One of the most commonly talked about fillers is dietary fiber. What is dietary fiber? Dietary fibers are carbohydrates that are resistant to mammalian digestion—aka carbs that humans and animals cannot digest with our own enzymes.

Let’s break this down a bit further.

False Idea #1: “Fillers are just there for bulk”

Fiber as an actual “filler” in the sense of filling up the digestive tract is important for both humans and horses. It helps maintain gut motility which is critical in keeping things regular. Gut fill is especially important for horses, because it maintains the integrity of their extended intestinal tracts. This is important for many reasons, especially for reducing the risk of a colic episode.

False Idea #2: “Fillers have no nutritional value”

For horses, fiber goes far beyond filler. This seems like the right place for the corny idiom I use in every blog post. “Hay is for horses.” The reasoning behind this phrase is that hay provides fiber, which horses—more specifically the microbes in the hindgut—use as an energy source. Unlike people, horses’ ability to digest fiber means that the fiber is contributing significantly to the nutritional needs of the horse. In fact, horses consuming primarily hay will meet nearly 80% of their energy needs from the fiber in that hay! I’d say that contributes nutritionally!

What about other ingredients in your horse feed?

My litmus test to determine if an ingredient is a filler follows a couple of steps:

1. Does it offer nutrition to the horse?

If a horse can use an ingredient for energy or nutrient requirements, I generally do not consider it to be a filler ingredient. Rehashing our previous discussion, the #1 filler in human food is dietary fiber, which is the #1 nutrient horses need. As much as we may have all been teased for being horse girls, we are not our horses.

Perhaps a more nuanced question is if the feed offers relevant nutrition to the intended class of horse. In a performance feed, oats are a source of calories and more specifically, a source of starch, essential for horses exerting energy and doing work. Using oats as the base for a ration balancer makes less sense because the target horse for ration balancers is typically a horse who does not need extra calories or additional starch in the diet. However, in either formula, it’s important to remember that oats are not 100% starch. They also contribute protein, fat, fiber, vitamins, and minerals.

What about balancers that contain more than just soybean meal, vitamins, and minerals? Wouldn’t anything additional be a filler? Again, it’s nuanced. In order to hit that 30% crude protein sweet spot that is an appropriate amount for the feeding rate, we need to combine soybean meal with another base ingredient. We then must consider what ingredient to use and what benefit it offers that target horse. Alfalfa is one of my favorite base ingredients because it is a great source of many nutrients including protein, fiber, and minerals. Specifically, alfalfa is a good source of calcium which allows us to reduce the amount of added calcium, thus improving pellet quality and taste.

The takeaway message here is that unless you are feeding a pile of ash (which I don’t recommend), everything is made up of nutrients. At Woody’s we are very intentional about which ingredients we combine together in a formula to provide precise, relevant nutrition for all classes of horses.

2. If an ingredient doesn’t support the horse nutritionally, is there another reason for inclusion?
   • Many of the nutrients that horses need are not tasty on their own. Adding flavors, or ingredients high in the target nutrient that are naturally palatable, goes a long way to ensure a horse will eat what you need them to.
   • Accuracy and Safety. Many micronutrients are needed in very small amounts (think less than one pound in a two-thousand-pound batch). Using a carrier ingredient helps the small but essential nutrients disperse evenly into the mix so that you know each pound of feed is the same as the next. If a nutrient like selenium is not distributed evenly through the batch, it could lead to a deficiency or a toxicity, depending on where your scoop lands in the bag!
   • Ease of use. Both in supplements and regular feeds, precision allows us to optimize formulas for horse health. However, precision often means irregular numbers that are tricky to measure out consistently or to get a standard scoop for. Using carriers allows us to effectively round up the math without sacrificing precision nutrition.
   • Other non-nutritive components. Additives that enhance shelf life may not contribute nutritionally to the formula, but they go a long way in reducing waste and giving you increased flexibility to store feeds.

In summary, if we consider a filler to be an ingredient that doesn’t contribute anything to the formula, there really aren’t fillers in horse feed. Sure, if you want to pick a fight, there are specific ingredients used in horse feed that don’t directly impact the horse. However, I argue that safety, shelf life, useability, and your wallet are all very important considerations as well.

What about by-products?

Since you’ve made it this far, I want to talk about another related topic that is near and dear to my heart… by-products. While well-intentioned, the decision to go with the term “by-products” has been met with some unfortunate and undeserved negative attention. Many horse people consider by-products to be “just fillers” that feed companies use to save costs. By-products are actually secondary ingredients that come from processing primary ingredients intended for human use. This does not mean that they lack nutrition or are inherently bad for the horse. The reality is that by-products are some of my favorite ingredients because of what they offer the horse.

A good example of this is beet pulp. Beet pulp is the by-product of the sugar beet industry. Sugar beets are used to supply about 55% of the United States sugar supply. Beet pulp is the material leftover after extracting all possible sugar from the beet. It is in the financial interests of the processing plants to remove as much sugar as they can from the plant, which means that beet pulp is actually quite low in sugar. What does beet pulp offer to horses?

On average, beet pulp contains moderate crude protein (9%), high crude fiber (19%), and low NSC (12%; 11% WSC + 1% starch). It is also a good source of calcium (1%) and at about 1.15 MCal/lb. digestible energy (DE), so it contains more calories per pound than both average grass and alfalfa hay. More importantly than just the crude fiber value, beet pulp is high in soluble fiber. This is the magical fiber that is more easily broken down compared to insoluble fiber but digested more slowly than starch and simple sugars. I consider beet pulp to be a super food for horses.

Many other ingredients commonly used in horse feed include:

• Soybean meal. Soybean meal is the most widely used source of concentrated protein for horses because of its favorable amino acid profile, availability, palatability, and ease of use (because pellet-ability isn’t a real word).
• Soy hulls. Like beet pulp, soy hulls are an excellent source of soluble fiber that supports ideal gut health and provides energy for the horse.
• Wheat midds. These are made up of the bran and germ of the wheat grain. Because the endosperm has been removed for flour production, the remaining “midds” are lower in starch and high in protein and fiber. Not only are they nutritionally advantageous, wheat midds also pellet easily, meaning that the formula may require lower amounts of additional binding agents.
• This is another by-product of the sugar industry. Raw cane and beet molasses are both much lower in sugar than many people realize, again because of the financial interests of the sugar companies. Molasses has been used for centuries in horse feed because of its palatability and ability to keep other ingredients from sorting.
• Rice bran. Rice bran is a by-product of the rice production industry and is a good source of both fiber and fat. At about 20% fat, rice bran is an easy way to boost the caloric content of your horse’s ration without adding much more volume.

What do all of these ingredients have in common? They serve a purpose for the horse. That’s why we we’re all here right? To do best by our four-legged friends. Please don’t be scared or led astray by commotions over fillers or by-products. Those of us formulating horse feeds trust these ingredients to feed our own horses, and you should too!