Providing your horse vitamins and minerals

Minerals are inorganic nutrients that horses need in relatively small amounts.

The essential major minerals include:

• Calcium (Ca)

• Phosphorus (P)

• Magnesium (Mg)

• Sodium (Na)

• Chloride (Cl)

• Potassium (K)

• Sulfur (S)

Trace minerals are minerals horses need in an even smaller amount. The essential trace minerals include:

• Iron (Fe)

• Zinc (Zn)

• Copper (Cu)

• Selenium (Se)

• Manganese (Mn)

• Iodine (I)

• Cobalt (Co)

A horse's mineral requirements vary based on the following.

• Bodyweight

• Age

• Physiological condition (e.g., pregnant, lactating)

• Activity level

For example, late gestation mares, lactating mares and young, rapidly growing horses require more of some minerals (e.g. Ca, P, Cu, Zn) than other horses.

The National Research Council’s (NRC) “Nutrient Requirement of Horses” lists daily mineral needs and mineral content of common feedstuffs. With little change in mineral content for most grains, you can use the NRC values. Forage mineral content can change greatly with soil type, species, maturity at harvest, etc. It’s best to test your forage to determine its mineral content.

Mineral deficiencies occur when horse’s receive less minerals than recommended. But providing too many minerals can result in toxicity. Not only must you consider the amount of minerals you provide, but also their ratios to one another and other parts of the ration.

Calcium to phosphorus ratio

An important ratio in mineral nutrition of the horse is the Ca to P ratio (Ca:P). The Ca to P ratio should be about 2:1, where there’s twice as much Ca as P. If horses receive adequate P, this ratio can range from:

• 1.5:1 to 3:1 in young, growing horses

• 1:1 to 6:1 in mature horses  

A ratio less than 1:1, where the P content exceeds the Ca content, can lead to orthopedic or bone disorders especially in young, growing horses. This can happen even if the total amounts of Ca and P are adequate.

Make sure you know the Ca and P content of all feedstuffs so you can achieve the proper Ca:P.  The Ca and P content in forages can vary. Legumes usually contain more Ca than grasses. Grains are usually higher in P and lower in Ca.

Other major minerals

High quality forages usually contain enough Mg, K and S.

You can meet your horse’s Na and Cl needs through salt. But a performance horse that sweats a great deal may need added K, Na and Cl to replace excess mineral loss from sweating.

Trace minerals

Trace minerals are essential to the horse. Trace mineral content varies in feedstuffs. Thus, you should have your feedstuff tested if you plan to formulate a ration from common feedstuffs alone. Some trace minerals interact with each other and can hinder their use by the horse. For example, high levels of ZN can hinder CU use, even if CU needs are met.

Selenium (Se) has a narrow range of daily intake in which it meets the horse's need. Above this range, Se can be toxic to your horse. Thus, you should know your horse’s trace mineral needs and meet them without over or underfeeding them.

It’s practical to use mineral supplements to meet your horse’s needs. The safety margin for most trace minerals is fairly wide. This allows you to use a mineral supplement with normal feedstuffs without risk of going over the maximum tolerance levels. You can provide minerals a number of ways.

Trace mineral salt 

Trace mineral salt can either be in block or loose form. It should contain Na, Cl and trace minerals but not Ca or P. With this approach you must make sure the rest of the ration meets the Ca and P levels and the Ca:P ratio for your horse.

Take care to select a trace mineral salt. Trace mineral content varies greatly with different mixes.

If you provide free choice trace mineral salt, don’t provide other sources of salt.

Encourage free choice intake of trace minerals to make sure your horse meets their needs.

• A loose form of trace mineral mix increases intake by 15 percent.  

• Place the mineral supplement holder in areas where horses gather.

• You can also add flavorings, such as dried molasses.

• Keep the mineral mix fresh. High humidity in the summer can cause clumping, which reduces intake.

You want your horse to eat about 1.5 to 2 ounces daily. If your horse doesn’t eat enough supplement, try moving the mineral mix holder or using additives to encourage intake.

This approach to providing minerals is the least dependable. Each horse will eat a different amount and it’s hard to measure how much each horse receives.

Commercial complete mineral supplement

Commercial complete mineral supplements contain major and trace minerals. Choose the supplement that compliments the remainder of your horse’s ration (e.g. hay and concentrate).

Feed the complete mineral supplement daily at the recommended rate to each individual horse. This approach makes sure each horse gets the correct amount of mineral.

Allow horses access to a white salt block that doesn’t contain trace minerals.

Commercial grain mix

Commercial grain mixes should contain major and trace minerals. Feed at the recommended rate to make sure the horse gets the correct amount of minerals. If you feed a lot more or less than the recommended rate, you’ll be either over or underfeeding minerals, respectively.

Don’t add other feedstuffs (oat, wheat bran etc) to a commercially prepared grain mix without understanding how it will affect the mineral content. These grain mixes have already been balanced for minerals. See Ration Balancer section below.

Allow horses access to a white salt block that doesn’t contain trace minerals.

Vitamin A (or precursor) and E are present at high levels in fresh green forages and newly harvested hay. Thus, grazing horses will meet their vitamin A and E needs.

During the winter, when hay is stored, vitamin A and E levels decline. You will need to supplement vitamins to meet their needs.

Vitamin supplements differ in chemical form as well as activity and stability. There are many commercial vitamin-mineral supplements and commercial grain mixes. Both options contain the necessary vitamins. Over feeding vitamins doesn’t present a problem. Thus, you can feed a vitamin supplement to grazing horses whose vitamin A and E needs are met.

Sun-cured forages contain vitamin D. Horses can also meet their vitamin D needs if they are in the sun for 4 to 6 hours a day.

The NRC doesn’t list daily needs for these vitamin K, C and B-complex because horses usually meet their needs through common feedstuffs and microbes in their gut. Thus, they don’t need a supplement.

Forage is the ideal energy source for horses. But most forages don’t meet the horse’s daily vitamin and trace mineral needs. If your horse gets enough energy from forages, you may consider feeding a ration balancer to provide vitamins and minerals the forage lacks.

Another example would be if you feed your horse hay and cereal grains (i.e. oats, corn) to meet their energy needs. In this case, you can feed a ration balancer because cereal grains aren’t good sources of the trace minerals and vitamins your horse needs.

Commercial feeds can replace the need for a ration balancer if each of the following are true.

• The feed is designed to provide all of the essential vitamins and minerals.

• You are following the manufacturer’s instructions when feeding it to your horse.

  • Feeding directions are listed on the feed tag or feed bag of the product.

Say you don’t follow the feed directions and decide to reduce the amount you feed. Not only will you be reducing the energy content of the diet but also the amount of vitamins and trace minerals your horse consumes. In this case, your horse’s diet now lacks trace minerals and vitamins. Similar cases are common when horse owner’s try to cut feed costs or manage their horse’s weight.

Following feed directions also means matching the commercial feed to the type of horse you’re feeding. For example, feed performance horses a feed specifically for performance horses and feed broodmares a feed specifically for broodmares.

You can choose a ration balancer based off the kind of hay you feed. The two basic types of ration balancers are:

• Ration balancers designed to be fed with grass hay or a grass-legume (i.e. alfalfa, clover) mix

• Ration balancers designed to be fed with legume hay  

Always follow the manufacturer’s feed directions when feeding a ration balancer. While the cost may seem higher compared to other commercial feeds (on a pound per pound basis), you will be feeding much less daily. Calculate the daily cost for an accurate comparison.