Of all the ingredients of a horse’s diet, minerals are unique. They contain no carbon, which makes them inorganic molecules. In fact, essentially, they’re rocks and it can be difficult to imagine their being digested by a horse. But minerals are an essential part of the diet, despite the fact that, like vitamins, they contribute no energy whatsoever. Without their participation, horses could not metabolise fats, proteins, or carbohydrates; their muscles and nerve would not function normally, and their bones could not support their own weight. Minerals help; the blood transport oxygen through the body, maintain the body’s acid/base and fluid balances, and are necessary components of virtually every enzyme the horse needs for everyday metabolism. They are integral parts of some vitamins, hormones and amino acids. Yet they make up only about 4% of the horse’s total body weight as compared to 30-35% fats, carbohydrates and proteins and about 60% water. In the case of minerals, a little bit means a lot.
Calcium and Phosphorous – first on the feed tag and in most discussions of minerals, is calcium, a versatile player best know for its role in bone structure and repair. Calcium makes up about 35% of the horse’s bone structure, but also is involved in a host of other functions, including cardiac muscle contraction, cell membrane integrity, glandular secretion, temperature regulation and blood clotting mechanisms. The absorption efficiency of calcium seems to decline with age and to range from as high as 70% in young horses, to 50% less in older ones. Under most circumstances, horses eating forage hay have a hard time developing a calcium deficiency, as hay (especially legume hay) is calcium rich: however, a diet very low in forage and high in grains (which are naturally high in phosphorous) can produce these symptoms. Historically, horses fed diets rich in wheat bran often developed this imbalance today it’s rare. One of the few other causes of calcium deficiency in horses is the ingestion of plants containing high amounts of oxalate compounds, which inhibit calcium absorption. Plants like sorrel, dock, rhubarb, purslane, Kikuyu grass and lambs quarter can contain potentially harmful amounts of oxalates. They are primarily a problem for young horses, and also can cause diarrhoea and gastroenteritis.
Potassium – Potassium designated by the chemical symbol K, is a crucial element of cellular osmotic pressure and the maintenance of the body’s acid/base balance. It also is considered an electrolyte, and is usually the other major mineral horse owners are concerned about replacing when a horse is working hard. Without sufficient potassium, horses are prone to fatigue, muscle weakness, exercise intolerance and decreased water and feed intake. Increased restlessness and spookiness, especially in response to loud noises also have been reported. Because sweating increases potassium loss both in the sweat itself and in the urine, deficiencies are a particular concern for high-level three-day event and endurance horses, particularly when they are training or competing in hot, humid conditions. Potential potassium losses also can be aggravated by the administration of diuretics such as Lasix (often used to treat racehorses with pulmonary haemorrhages, sometimes called “bleeders”) and are a risk in horses with diarrhoeal diseases such as Potomac horse fever.
Magnesium – About 60% of the body’s store of magnesium is tied up in the skeletal structure, but it also is an important activator of many enzymes. Fortunately for the horse, his magnesium needs of about 0.1% per day are easily met by a normal diet (the magnesium content of most horse feeds is between 0.1%- and 0.3%). Magnesium absorption tends to be in the 40% range, with utilization of added dietary sources, such as magnesium oxide or magnesium sulphate sometimes somewhat better (up to about 70%).
Sulphur – We don’t tend to think of sulphur as an important mineral, bit it is an essential constituent of several amino acids (methionine, cystine, and cysteine) as well as the B vitamins biotin and thiamine, and a number of other important molecules such as insulin, taurine and chondroitin sulphate (a component of cartilage, bone, tendons and blood vessels). The concentration of sulphur in the body is highest in hooves and hair, which both contain the protein keratin (4% sulphur). Overall, it makes up about 0.15% of the horse’s total body weight.
Trace Minerals – Selenium – Although it is needed in infinitesimal amounts, selenium is a mineral that has received a lot of press in recent years. Selenium and vitamin E function in a partnership that helps protect body tissues from free-radical damage that occurs during oxidation (the conversion of feedstuffs into energy). In particular, they act as a defence mechanism against damage to cell membranes and enzymes. While vitamin E blocks free radical attacks on lipids, selenium is a component of the enzyme glutathione peroxidase, which helps prevent the formation of free radicals and destroys lipid peroxidases that are released into the cells. The dynamic duo works best when both are present in the correct amounts.
Iodine – Iodine is a specialist. It is essential for the synthesis of thyroid hormones thyroxin (T4) and triiodothyronine (T3), which help regulate basal metabolism and unlike some other minerals, which fulfil numerous functions, this is iodine’s only known role in the diet.
Copper – This mineral is a component of several enzymes involved in the syntheses and maintenance of elastic connective tissue, the mobilisation of iron stores (more on iron in a moment) and synthesis of the body pigment melanin, as well as being involved in bone collagen stabilization. Copper deficiencies can play a role in development orthopaedic diseases of young horses (although some researches now believe it’s participation might have been over-rated), and it also has been implicated in rupture of the aorta or uterine arteries in aged foaling mares.
Iron - Most of us are familiar with iron’s role in haemaglobin, the molecule in red blood cells that enables them to transport oxygen throughout the cells of the body. Approximately 60% of the body’s iron is involved in this task, with another 40% incorporated in muscle myoglobin, storage forms and various enzymes. The horse’s estimated iron needs are about 50ppm per day for pregnancy and lactation, and for growth and 40ppm for other mature equines. Most forage contain between 50 and 250ppm (occasionally, up to 400ppm) of iron, so under most conditions horses receive plenty of iron in their normal diets, and clinically recognised iron deficiencies rarely occur in either foals or mature horses at any performance level. Only under conditions of severe or chronic blood loss is an iron deficiency likely; sometimes this blood loss is not obvious (it might be the result of a severe intestinal parasite problem, or even a serious case of lice).
Zinc - The metabolism of proteins and carbohydrates is assisted by a number of enzymes containing zinc. The absorption of this mineral can vary widely and the level of many other minerals, including copper and iron, affects it. Forty ppm of zinc per day has been recommended for adult horses, and a higher level might be beneficial for foals. Zinc is considered as playing a role in growth and the prevention of developmental orthopaedic disorders, but to what extent no one is sure.
Manganese – Lipid and carbohydrate metabolism depend on manganese and this mineral also is essential for syntheses of the chondroitin sulphate needed for the synthesis of the chondroitin sulphate needed for cartilage formation. These are function involved mostly in reproduction and growth. The exact amount of manganese needed by horses has not yet been determined, although based on other species, 40ppm per day is generally considered ample. Although manganese deficiencies sometimes are a problem in ruminants, they have not been described in horses. If such a deficiency did occur it would likely result in fertility problems in adult breeding stock and limp deformities in foals. More good news no harmful level of manganese has been established for horses, who seem to be able to tolerate large quantities of the mineral with no ill effects.
Cobalt – Cobalt’s only known function is as a component of vitamin B12 so a cobalt deficiency results in a B12 deficiency. Based on levels recommended for cattle. A minimum of 0.1 ppm of cobalt and a maximum of 10 ppm, is suggested for horses, but neither deficiencies nor excesses of this mineral (nor of vitamin B12) have been described in horses as yet. Most researches suspect that neither is likely to occur.
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Information for educational purposes only.
