Vitamin and Mineral Nutrition of the Horse

Minerals are inorganic nutrients that are needed in relatively small quantities by the horse. The essential major minerals are calcium, phosphorus, magnesium, sodium, chloride, potassium and sulfur. The essential trace minerals needed are iron, zinc, copper, selenium, manganese, iodine, and cobalt.

A horse's mineral requirements will vary based on its body weight, age, physiological condition (e.g., pregnant, lactating) and activity level. For example, late gestation and lactating mares as well as young, rapidly growing horses have a proportionally greater requirement for some specific minerals e.g., calcium, phosphorus, copper, and zinc, than do other horses. The National Research Council (NRC) 2007 publication entitled, Nutrient Requirement of Horses lists daily mineral requirement as well as the mineral content of common feedstuffs. The mineral content of most grains and supplements are consistent enough that you can use values in the NRC tables; however, the quantity of minerals in forages can vary significantly with soil mineral content, plant species, stage of maturity at harvest, harvest conditions etc. Consequently, forages should be sent to a laboratory for mineral analysis.  This can be done for a small fee of $10 through NCDA&CS Farm Feed Testing Service.  Check with your Extension agent for more information.

Providing minerals at less than the recommended quantities can result in a dietary deficiency whereas providing minerals in excessive quantities can result in toxicity. In addition to the amount of mineral required daily, the ratios of minerals with each other and with other components of the ration are important due to effects on absorption, metabolism and/or excretion. In particular, a critical consideration in mineral nutrition of the horse is the calcium to phosphorus (Ca:P) ratio. 

Although the quantity of trace minerals required for normal growth, development and metabolism is very small, they are all absolutely essential.  Providing mineral supplementation can be accomplished in a number of different ways. You can use:

1.  Trace mineral salt, either in block or loose form containing Na, Cl and trace minerals but no Ca or P. This approach assumes that the Ca and P levels as well as the Ca:P ratio provided in the rest of the ration are appropriate. 

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2.  Commercial complete mineral supplements containing major minerals such as Ca, P, Na, Cl, trace minerals etc. The mineral supplement should be chosen to compliment the mineral content of the remainder of the ration e.g., type of forage and concentrate if any. The complete mineral supplement is fed daily at the recommended rate to each individual horse. This method ensures that each horse consumes the appropriate amount of mineral. When using a complete mineral supplement horses should also have access to a white salt block that does not contain trace minerals.

3.  Commercial grain mix which contains major and trace minerals. If fed at the manufacturer's recommended rate, this method ensures that each horse consumes the appropriate amount of mineral.  When using a commercial grain mix, horses should also have access to a white salt block that does not contain trace minerals.

Vitamins are organic compounds that are needed in even smaller quantities than minerals by the horse, although no less critical. Vitamins can be divided into two groups, the fat soluble vitamins A, D, E and K and the water soluble C and B-complex vitamins. The National Research Council (NRC) 2007 publication entitled,Nutrient Requirement of Horses lists estimates of the daily requirements for vitamins A, D, E, and the B-vitamins thiamin and riboflavin. 

Vitamin A (or its precursor beta-carotene) and vitamin E are present in high concentrations in fresh green forages or newly harvested hay. Consequently, a horse grazing pasture will meet its vitamin A and E requirements. However, during the winter, when hay is stored, the levels of vitamins A and E in hay drop significantly, necessitating supplementation to meet requirements.  Sun-cured forages contain vitamin D. The vitamin D requirement is also met if the horse is exposed to sunlight for four to six hours a day because the ultraviolet rays of the sun will convert a precursor present in the skin to vitamin D.

Source: Marcia Hathaway, PhD. Department of Animal Science, University of Minnesota

To view the full article click here: http://www.extension.umn.edu/agriculture/horse/nutrition/vitamins-and-minerals/