Vitamins are organic compounds required by horses in tiny quantities to maintain good health. They can be divided into two types:

  • Fat soluble — vitamins A, D, E and K, which can be stored in the body
  • Water soluble — B vitamins, biotin, choline, inositol and vitamin C

B vitamins are synthesised by micro-organisms in the hind gut and cannot be stored by the horse. Despite this B vitamin deficiencies are rare in healthy horses kept on a well-balanced, high-fibre diet, although horses in intensive training, such as eventers and racehorses, may benefit from supplementation

Vitamin B12 (cobalamin)

Use: Vitamin B12 is a complex vitamin vital for enzyme function and metabolism of fat, protein and carbohydrate. It is synthesised by micro-organisms in the horse’s gut and is also required for blood cell formation and the production of amino acids.

Signs of deficiency: Loss of appetite and faulty metabolism.

Folic acid (folate)

Use: This was formerly known as vitamin Bc and works closely with vitamin B12 to produce red blood cells and haemoglobin.

Signs of deficiency: Poor growth and anaemia, although deficiency is rare in horses.

Vitamin B6 (pyridoxine)

Use: This vitamin affects the nervous systemand is essential for energy production, the metabolism of protein and carbohydrates, nervous system activity, production of blood, plus protein breakdown and build up.

Signs of deficiency: Faulty metabolism within the gastro-intestinal system, loss of muscular tone and nerve coordination, roughened coat.

Vitamin B1 (thiamin)

Use: This vitamin is required for fat and carbohydrate metabolism and deficiencies can result in anxiety, stress and lack of energy. It is often incorporated into supplements as a calmer.

Signs of deficiency: Anaemia, bladder incontinence due to nervous irritability, capillary weakness in the blood vessels, nervousness and irritability, dry skin and staring coat. Also gastric disturbances,skipped heartbeats or abnormal slowing of the heart rate (bradycardia), loss of appetite and weight, ovulation problems in mares.

Vitamin B2 (riboflavin)

Use: Vitamin B2 is vital for the metabolism of proteins and carbohydrates and nervous system function, and is found naturally in leafy, green hay.

Signs of deficiency: Tongue ulcerations, degenerative changes within the colon, eye problems such as cataracts, faulty carbohydrate metabolism, inflammation of gums, secondary anaemia within the blood vessels.

Vitamin B3 (niacin: nicotinic acid and nicotinamide)

Use: Niacin promotes healthy skin and digestion, and is important for the metabolism of carbohydrates, fats and proteins.

Signs of deficiency: Anaemia within the blood vessels, digestive disturbances, loss of appetite.

Vitamin B5 (pantothenic acid/pantothenate)

Use: This is required for the production of antibodies for immunity, and also the metabolism of carbohydrates, fats and proteins.

Signs of deficiency: Can result in skin disorders and weight loss.


Use: Sorbitol is a carrier, specifically for vitamin B12, and enhances vitamin absorption.

Signs of deficiency: Deficiency in horses is rare.

Choline and inositol

Use: Choline and inositol are vital for a healthy liver and help the breakdown of fat, resulting in healthy hooves and coat and the elimination of toxins.

Signs of deficiency: Deficiency in horses is rare.

BiotinUse: Part of the B vitamin group, biotin is necessary for the metabolism of protein, fat and carbohydrate and increases production of keratin in the hoof by breaking down protein.

Signs of deficiency: Poor hoof growth, heel cracks, fissures and ridging of the hoof wall.

Read this full feature, including advice on whether your horse would benefit from B vitamin supplementation, in the July issue of HORSE magazine, OUT NOW!

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