Excerpt from Chapter 20 – Athletes
An athletic horse brings to mind one with speed, control, endurance, and the ability to focus, who is in top shape, muscular, and healthy, where every cell in his body works together to bring about the perfect form. His performance may be before the crowds or just between the two of you as you ride the trail, practice in the arena, or work on the farm. Whatever purpose you’ve given him, he relies on you to give him the best food, sufficient rest, and the care he needs to be your devoted partner.
Your athletic horse’s nutritional needs are enhanced, though they’re not especially different from other horses’. But the more work we ask of him, the more nutrients he needs to do the job and recover so he’s fit enough to do it again and again. This chapter examines how the diet should change when we ask him to work harder, to keep him sound and prevent injury.
The goal is to optimize his ability and performance so you — and he — can take pride in your shared accomplishments.
VARIATIONS BETWEEN ACTIVITY LEVELS
Before we discuss individual nutrients, I’d like you to see how your horse’s requirements change the more exercise he does. Using the nutrient requirements of an 1100 lb (500 kg) horse as an example, take a look at the trends rather than the exact amounts, since your horse’s weight may be considerably different.
Table 20-1 shows you the requirements for six key nutrients. Keep in mind that these are minimum requirements and your horse may be getting more than the table indicates. In most cases, that is perfectly fine; certainly it is for the nutrients shown in Table 20-1. However, some minerals, such as iron, zinc, and copper, need to be in proper proportion to one another to prevent competition for absorption sites within the digestive tract. And others, like selenium and iodine, are toxic in high doses. I’ll discuss these later in the chapter as I go through each nutrient classification.
For the most part, I’ll be speaking in generalities rather than giving you exact amounts to feed. There are as many combinations of ingredients as there are horses, so my goal is to arm you with information so you can create the best diet for your horse’s particular circumstance.
The term energy is synonymous with calories. It’s called digestible energy (DE) because it doesn’t account for fecal losses, but only for what actually gets absorbed into the blood stream. Your horse uses DE to do work, but it is also needed to sustain internal organs, secretions, digestion, and a multitude of bodily functions. Some of it is even given off as heat. But the bottom line is… the more your horse exercises the more DE he needs to maintain a normal body condition, inside and out.
If DE is insufficient, your horse will use his available stores for exercise, and actually mobilize (remove) nutrients from his own body tissues to meet the additional demands placed upon him. He’ll lose body fat and muscle mass, and his bones will thin. So it is critical for his health that his maintenance requirements be met first, followed up by additional calories for exercise.
For those of you who like to crunch numbers, the digestible energy calculations that follow3 can help you decide if your horse is getting enough calories to meet his work requirements. To use these formulas, you’ll have to convert your horse’s weight from pounds to kilograms; simply divide lbs by 2.2. For example, an 1100 lb horse weighs 500 kg (1000 divided by 2.2 = 500).
Protein has calories, but it should never be used to meet your horse’s DE requirement. Leave that to the carbohydrates and fat in his diet. Instead, protein should serve as a source of amino acids that your horse can use to build the proteins that his body needs. When we add protein to our horse’s diet, we generally think of building muscle mass, but that’s only one of hundreds of proteins in his body. Each tissue, whether it is muscle, bone, blood, liver, heart, arteries, skin, hair, hooves — the list goes on and on — has its own specific proteins which are made up of long, branched chains of amino acids. So the goal in feeding protein is to make sure that your horse has all the building blocks (amino acids) he requires to build and replace body tissues.
A protein source that has all the essential amino acids in proper proportion is considered complete and referred to as a high-quality protein. Chapter 4 — Fundamentals of Protein and Amino Acids discusses this in detail. But I’m not suggesting that you evaluate each feed for its amino acid content. Instead, you need to know just one simple rule: add a legume to cereal grains or grass to create a high-quality protein.
There are two commonly fed legumes — alfalfa and soybean meal. Soybean meal is actually much better because it comes very close to being a perfect protein source, with all the amino acids in their right proportion. Alfalfa is not as good, but still worthwhile, and boosts the overall protein quality of your horse’s forage intake.
If a legume is not added to your horse’s meal, the overall diet will likely be low in several amino acids. The one that tends to be the most limiting (low) is lysine. That’s why you’ll often see it added to horse feeds and supplements. But there are others that should be added and most commercial performance feeds will include methionine and tyrosine, as well as the branched-chain amino acids leucine, isoleucine, and valine. Your horse cannot produce these on his own; therefore they must be in his diet. If you mix your own ingredients, be sure to add a complete protein supplement to ensure that your horse is getting what he needs.
Take a look again at Table 20-1. Look at the crude protein and lysine requirements. As expected, they both rise as exercise gets more intense. But you need to be aware that crude protein is really just a measure of how many amino acids are in the feed; it tells you nothing about the specific ones or whether or not they’re in the right amounts.
Lysine requirements are shown to help you boost overall protein quality, but instead of adding a lysine supplement, add a legume to provide not only lysine but other essential amino acids. The overall protein intake should be 12-14% of the diet, and even more if your horse is still growing (see Chapter 19 — Growth and Growing Old).
Exercise Induced Pulmonary Hemorrhage (EIPH)
Any fast or intense exercise can cause the lungs to bleed. In mild cases you may not even notice it, and attribute your horse’s erratic behavior to nervousness.
In more extreme cases, however, there’s no missing the trail of blood coming from his nostrils. But no matter the severity, any blood in the lungs is a source of inflammation and potential infection. The more irritated and inflamed the horse’s lungs, the smaller the airways become, setting off a continuous cycle of bleeding with each subsequent performance.
There are many theories about the exact cause of EIPH, but there’s no doubt that poor nutrition can cause weakened capillaries. Add high blood pressure to the situation, which naturally occurs as heart rate increases, and it’s easy to see how these tiny blood vessels can rupture.
The way to prevent EIPH is to first take care of the lungs by providing clean air for your horse to breathe. Barns are notorious for fumes and dust. See Chapter 16 — Immunity Issues for ways to help your horse’s respiratory system stay healthy. Besides managing his physical surroundings, attention to his nutritional needs will make a difference. Ever know anyone who bruises easily — where just a slight bump causes a discoloration of the skin? That’s a sign of a vitamin C deficiency along with not enough protein. And it’s the same with your horses. Vitamin C produces the glue, collagen, that holds capillary cells together. If collagen production is diminished, capillaries rupture, plain and simple. Collagen is a protein; to make more your horse needs amino acids, building blocks of protein. If your horse’s diet contains low-quality protein, he will use what few amino acids he has to take care of more life threatening concerns — collagen production will be low on his list of priorities.
Please refer to Chapter 6 — Fundamentals of Vitamins for more information on vitamin C. Please pay attention to this vitamin. It is felt that supplementation
is not necessary because horses produce their own vitamin C (whereas we cannot). And it’s true — they can produce vitamin C but their need may exceed their supply when stressed, both physically and mentally.