MINERALS: Necessary in Small Amounts
Last month we looked at the role of the different vitamins, where they can be found, and what can happen if the horse has too little or too much. This month, we’ll do the same with minerals.
Minerals are found in forages, feeds, and supplements. Remember that minerals are inorganic: those found in forages have been taken up by the plant and the amount varies depending on the growing conditions. To make things confusing, some are listed as “organic minerals” because they are bound to an organic substance such as proteins or amino acids. This shouldn’t be confused with the foods that are labeled “organic” in the grocery store- different concept entirely! It’s thought that the “organic” minerals are more bioavailable, or more easily used by the horse.
Minerals are needed in small amounts. I’m not going to tell you how much your horse needs, as that is a conversation to have with your veterinarian. Every horse is an individual and should be fed as such. Your horse’s requirements will vary depending on his age, health, use, and other factors.
Sometimes it’s not the total amount of minerals that matters, but its proportion to other minerals. We talked about this previously when we touched on the concept of limiting factors in amino acids. You can think of one mineral or one amino acid as a key: using it unlocks the potential of other minerals. If you don’t have enough (or the key is too small for the lock), it won’t unlock and the other minerals can’t do their jobs. If you have too much (or the key is too big) the other minerals can be blocked. So…Goldilocks moment here…more isn’t better. Not enough isn’t good either.
Minerals are generally categorized into two groups: major and trace. “Major” does not mean that the horse needs large amounts of these minerals. “Trace” means that the horse needs smaller amounts of these minerals than he does of the “major” minerals. Not very helpful, right?
The minerals that are considered “major” are: calcium, phosphorous, sodium, chloride, magnesium, potassium and sulfur. We’ll quickly talk about what they do and where they are found in the horse’s diet.
Calcium and phosphorous work together as a team. This is a case where the proportion is as important as the amount. The ratio of calcium to phosphorous should be 2:1 ideally, or two parts calcium to one part phosphorous. This can vary depending on your horse’s age. Youngsters have a different need than mature horses. Talk with your vet, review your feed, and analyze your hay because it all matters when you are trying to develop good bone in a young horse. Even if your ratio is correct, your young horse can develop bone issues if he isn’t getting enough calcium and phosphorous.
In addition to being very important for bone development, calcium also aids in blood-clotting, heart rate metabolism, and muscle function. Luckily, the horse can tolerate a high amount of calcium as long as the phosphorous ratio is sufficient but check with your veterinarian if you have concerns. Phosphorous helps in the metabolism of carbs, fats, and vitamins, and helps with kidney function and the repair of cells. Important things! Calcium is found in grasses and legumes. Alfalfa tends to have a higher level than grasses. Phosphorous is also found in grasses but more so in grains such as oats and wheat bran. In fact, the calcium/phosphorous level in grains tends to be inverted, meaning that there is more phosphorous than calcium. Why does it matter? Because too much phosphorous is bad. It blocks the uptake of the available calcium and can lead to bone problems. Let me put this another way to help you remember. If you tell me that you feed oats and give bran mashes, I’m going to ask you, point-blank, what you are doing to correct the calcium/phosphorous ratio. And I’m going to stare at you until you give me an answer!
Sodium and chloride are two more major minerals that we can address as one, because we know the combination more commonly as salt. We could spend a whole article on salt but for now we’ll just say that the horse needs about two ounces a day to help regulate his blood, conduct electrical impulses to his muscles, trigger his need to drink, and keep all his body systems performing. Commercial feeds usually have only a small amount, so ALWAYS offer free choice salt. It can be either loose or in a brick form, but it should always be accessible. The horse will seldom take too much but he can tolerate an excess generally if he has access to clean, fresh water. If he does have too much salt, it can lead to diarrhea, hind-end paralysis, and even death. If he doesn’t have enough, he will display dehydration, muscle weakness, incoordination, and decreased ability to sweat. Salt deficiency can happen very quickly as the horse sweats so his intake is something you should monitor consistently. It is critical and the horse must have it.
Three more major minerals are magnesium, potassium, and sulfur. These are found in quality forages, but the plant’s ability to take up these minerals can vary depending on the weather, soil, and overall plant health. It isn’t feasible to test your horse’s pasture, but you can have your hay analyzed to determine the mineral content. Quality commercial feeds and ration balancers will also list the amount of these minerals.
There is a lot of research being done on magnesium in the horse’s diet, with some interesting results. Magnesium is one of the major minerals in bone, and it has a role in over 300 enzyme reactions in the horse’s body. It’s important in nerve function and in muscles. It works antagonistically or against calcium in contracting and relaxing muscles. We’re starting to realize that the calcium:magnesium ratio is important and should be between 2.5: 1 and 3:1. Luckily, most forages and commercial feeds provide adequate magnesium but if it becomes necessary to supplement, then the amount of calcium should be considered too. There is evidence that magnesium can help calm hot horses, but why is not fully understood yet. There are several types of magnesium, and the type of magnesium that you feed matters. Magnesium oxide is 50% absorbable by the horse and has the benefit of not overdosing, but magnesium sulfate, also known as Epsom salt, draws too much water into the horse’s large intestine and causes diarrhea. Please don’t assume that all magnesium supplements are the same because they aren’t.
Potassium is necessary for muscle function and acts with sodium and calcium to help muscles contract and relax. Most horses consume more than they need in their forage, so deficiency isn’t generally a concern. Horses can lose potassium very quickly through sweat and a deficiency can lead to dehydration. Feeding forage (and offering a constant supply of clean water) will help correct the situation. Because healthy horses can pass the excess as urine, it isn’t usually a problem…unless they have kidney problems, severe trauma, pain, or burns, have had a severe episode of tying up, or carry the gene for HYPP (hyperkalemic periodic paralysis.) That complex health concern is beyond the scope of this article. If you have a horse with HYPP, you should be in regular discussion with your veterinarian and you should be constantly monitoring your horse’s diet…and this means having your hay analyzed.
Sulfur is another major mineral that is found in forage, and in some places, in water. If your water contains a high level of sulfur, you may notice a rotten egg smell. Horses that are willing to drink this seem to clear the excess easily by passing it out in their urine and manure. However, it binds to calcium, so it can be of concern if your horse’s diet is high in calcium. Uroliths (mineral masses the resemble rocks) can form in the bladder and restrict or obstruct the flow of urine. Some of these can be passed by the horse, others require surgery. Sulfur is not well understood but seems to play an important role in healthy hoof growth. Deficiencies may show as poor hoof quality. That smell you notice during hot shoeing? Likely it’s sulfur gasses burning off.
Trace minerals are needed in small amounts but are still very important to your horse’s health. The ones that we’ll discuss here are iron, zinc, copper, selenium, manganese, iodine, and cobalt. Don’t worry- we’ll keep it short! In some cases, scientists are still researching the effects of these minerals.
Iron is usually abundant in soil, so the horse typically gets a sufficient amount in his forage. Iron deficiencies are not common, except perhaps in foals. Too much iron is usually not a cause for concern either because the horse’s body is very efficient at taking what it needs. A horse can become iron deficient due to prolonged blood loss though, and this can be critical because iron’s job is to help transport oxygen in blood. Check with your veterinarian before supplementing with iron as too much can interfere with the uptake of other minerals.
Zinc and copper are two more elements where the ratio is important. Although they have different functions, the method of absorption into the body’s circulation is similar so the proportions must be correct in order for the horse to make full use. The current thinking is that the ratio should be four parts zinc to one part copper for mature horses. (For foals and growing horses, you should talk with your veterinarian or an equine nutritionist.) Zinc is part of over 100 enzymes in the horse’s body which drive body functions such as the metabolism of proteins and carbs. It’s also important for eye and hoof health and proper bone development. Deficiency generally isn’t a problem, and horses can tolerate excess to a point, but too much interferes with the absorption of copper because of that important ratio we mentioned above.
Copper is important for the health of tendons and ligaments, cellular health, and pigment in hair, skin, and eyes. It also helps to mobilize the iron that a horse’s body stores. Deficiencies can result in abnormal bone growth in young horses and tendon and ligament issues in mature horses. Horses can tolerate an excess of copper, but it’s interesting to note that the more they consume, the less they absorb.
Zinc and copper are both found in forages. Here in the northeast, our forages tend to have low amounts. Zinc is also found in wheat middlings, brewer’s grains, and wheat bran. Copper is in molasses, brewer’s grain, and soybean meal. If your horse is on a forage diet, this is a great reason to add a ration balancer to make sure that he is getting enough of these minerals. Horses that are on quality commercial feeds and are being fed according to the recommendations (in pounds) are probably taking in an adequate amount.
Selenium is a tricky subject. We all think we know about selenium, right? We’ve been told that the soils here in the Northeast are deficient in selenium, so our forage is deficient, and that we should be supplementing. But wait a moment before you run out and buy a jar. Selenium is needed in very small amounts, and too much of it can be lethal. To complicate the matter, we aren’t really sure how much the horse needs. How’s that for confusing? Imagine that you have a dollar bill and you cut it into 1000 (yes, one thousand) equally sized pieces. The weight of maybe two of those teeny tiny pieces is what we think should be the amount of selenium that a horse should eat in a day. Don’t panic and dump your jar of selenium supplement though; read the label and feed accordingly. More on this later.
Selenium works with Vitamin E to neutralize free radicals and helps in the production of thyroid hormones that regulate metabolism. Too little can lead to weakness, respiratory distress, difficulty in swallowing and impaired heart function. Horses are very sensitive to too much selenium, which can cause diarrhea, sweating and shaking, increased respiration and pulse, colic, blindness and death. How much is too much? The lowest recorded lethal dose is the same weight as slightly less than two dollar bills. Obviously, there’s more to that measurement, but the point is that more is not better. If you have concerns, you should definitely speak with your veterinarian or an equine nutritionist.
Manganese plays an important role in helping the horse metabolize or use the fats and carbs that he consumes. It is also important in his ability to synthesize chondroitin sulfate, which is needed for forming cartilage. So before you start purchasing expensive joint supplements, make sure that his diet contains enough manganese. Then supplement if you must. There haven’t been any known cases of horses eating a toxic amount of manganese but it is thought that too much might interfere with the absorption of phosphorous. Manganese is found in forage, and good quality forage usually contains a generous amount. To be sure, have your hay analyzed. Manganese is also added to quality feeds and ration balancers.
Iodine is a mineral that you will find mostly in the horse’s thyroid gland, and it is critical for the synthesis of hormones. No, I’m not talking about moody mares and aggressive stallions- there are more hormones than those! Hormones can also affect metabolism and other body functions and iodine levels can be very sensitive. Too little or too much iodine, and your horse’s body chemistry can be seriously out of balance. Your veterinarian can test for iodine levels and help you create an appropriate diet. One of the best ways to increase the iodine in your horse’s diet is to offer iodized salt. Consult with your veterinarian regarding the amount though, because too much iodine is not good either.
Cobalt is interesting because it is needed by the bacteria in your horse’s hindgut to produce Vitamin B12, and Vitamin B12 works with iron and copper in the formation of red blood cells. It is found in forage. While there haven’t been any documented cases of a cobalt deficiency, it’s been noted that feeding more cobalt benefits the bacteria, which then help the horse to make better use of his forage. (I don’t know how they study that, but it must involve studying manure!)
How can you tell the amounts of minerals in your horse’s feed? First, have your hay analyzed. It won’t likely give you results of all the minerals but it’s a good place to start. In some cases, the amounts may be estimated. Then look at your feed bag. A least cost ingredient “value” feed will probably only list calcium and phosphorous and maybe salt, copper, selenium, and zinc. It doesn’t mean that there aren’t other minerals present, just that the amounts aren’t guaranteed. You really don’t know how much your horse is getting. Fixed formula and fixed nutrition feeds will give you more information. Of course, those feeds cost more too!
Calcium and phosphorous are listed as a percent, which is the percent in the total bag. Other are listed in ppm or parts per million. Now this is where it gets confusing. PPM means milligrams per kilogram. So if you are feeding a kilogram of ABC feed that contains 120 ppm of zinc, then your horse is getting 120 milligrams of zinc from the feed. But if you look at the feed tag, the feeding recommendation is in pounds! You’ll need to convert kilograms to pounds. In this case it is 120 mg in 2.2 pounds of feed.
Supplements can trickier. Hopefully the label will tell you how many milligrams are contained in a scoop, but the serving size may be in grams or ounces. ALWAYS use the scoop that comes with the product, and read the label to make sure that you are giving the proper serving size per day. Don’t use the scoop from one supplement to measure out another supplement because the scoops are probably different sizes. A scoop of ABC Joint Supplement may weigh more or less than a scoop of XYZ Respiratory Aid. Don’t assume that one-ounce scoops are all the same, because the density of the product may be different. It’s like using a 14-ounce coffee can to measure both coffee and rocks. It can hold 14 ounces of coffee, but it can hold several pounds of rocks, depending on the size of the rocks.
Why does that even matter? Take a moment and re-read the paragraph about selenium. If you are supplementing with selenium and you aren’t using the scoop that came with the product, you could be underdosing or overdosing. Because the safe range for selenium is small, and because the amount that the horse needs is small, this could have serious consequences.
Our take-away message this month is this: horses need minerals in small amounts. Read your feed and supplement labels, follow the directions, and remember that more isn’t always better. If you are feeding a quality feed or ration balancer, you may not need to supplement. Consult your veterinarian if you have questions.