Vitamin Functions, Deficiencies, & Toxicities in Horses

Understanding what functions vitamins have on your horses body can help identify whether your horse has either a deficiency, or is possibly overdosing.

Functions and deficiency signs of vitamins (BASF 2000):


Major Function

Signs of Major Deficiency

Vitamin A Vision, mucous tissue integrity, immunity Xerophthalmia, tissue keratinization, polyneuritis, hind leg paralysis, elevated cerebrospinal fluid pressure, ataxia, depressed immune system, reduced fertility
Vitamin D Calcium and phosphorus balance Rickets, osteomalacia, metabolism, bone calcification, immunity
Vitamin E Intracellular respiration, antioxidant, membrane integrity Encephalomalacia, depressed immune status, skin edema, steatitis, jaundice, liver necrosis, anemia, erythrocyte hemolysis, muscular dystrophy, fetal death, reduced fertility
Vitamin K Blood coagulation Prolonged blood clotting, low prothrombin, intramuscular bleeding, anemia, hemorrhage
Vitamin B1 (Thiamine) Metabolism of carbohydrates and proteins, nervous system Loss of appetite, polyneuritis, skin edema, fatty liver, fatty heart, convulsions, cyanosis, gastrointestinal hemorrhage, diarrhea
Vitamin B2 (Riboflavin) Antioxidant, H-transfer, ligament integrity Poor growth, shortened bones, curled toe paralysis, fused ribs, dermatitis, poor hair coat, seborrhea, photophobia, cataracts, anemia, stiff crooked legs, fetal death, reduced fertility, collapsed ovarian follicles, diarrhea, anal mucosa inflammation, ulcerative colitis
Vitamin B5 (Pantothenic Acid) Conversion of amino acid groups as coenzyme A, skin integrity Dermatitis in feet and mouth, blindness, goose stepping, demyelinization
of spinal cord, depressed immune system, decreased milk production, embryo detachment, diarrhea, GI ulceration, fatty liver
Vitamin B3 (Niacin) Metabolism of carbohydrates, protein and fats, H carrying enzymes NAD and NADP, skin integrity Bowed legs, diarrhea, general dermatitis of feet and mouth, anorexia, hind leg paralysis, GI ulceration
Vitamin B6 (Pryidoxine) Metabolism of proteins Dermatitis around the eyes, fatty liver, ataxia, convulsions, diarrhea
B Complex (Choline) Methyl donor group, phospholipids Poor growth, fatty liver, enlarged
spleen, abnormal gait, demyelinization of peripheral nerves, depressed immune system, reduced fertility, kidney damage
Vitamin B12 (Cyanocobalamin) Protein metabolism, transport of methyl groups Anemia, poor growth, poor hair coat, fatty kidney, kidney damage, ataxia, uncoordinated hind legs, impaired thyroid, diarrhea
Vitamin B9
(Folic Acid)
Transfer of single carbon units
in activated form for methylation reactions involving methyl donors such as methionine and choline, immunity Poor growth, anemia, poor skin condition, reduced fertility
Vitamin B7 (Biotin) Metabolism of fats, carbohydrates and proteins as coenzyme for
CO2 fixation and transcarboxylation General dermatitis, dermatitis on feet, mouth and eyes, poor hair coat, weak- walled brittle hooves, spasms in hind legs, stiff gait, reduced fertility
Vitamin C Antioxidant, hormone synthesis, conversion of vitamin D3 to calcitriol, essential for bone calcification Poor hair coat, depressed immune system, hemorrhage, delayed wound healing, degenerated enlarged adrenal, scoliosis,

Note: Only add vitamin supplements to your horses feed if need be as there are a number of issues with overdosing.

Common Vitamin Overdoses/Toxicity:

  • Vitamin A toxicity is most common with symptoms that include slowed growth, dull coat, depression, alopecia sever bone deformation and eventually death.
  • Symptoms for Vitamin D toxicosis are depression, low appetite, weight loss, stiff limbs. Chronic toxicity symptoms include calcification of kidneys, rarefaction of bone, sever weight loss and death.
  • A Vitamin C overdose can result in diarrhea, iron toxicity, anemia, and liver problems.

Here is a table of the recommended vitamin value per day:vitamins table

I hope this helps 🙂

One thought on “Vitamin Functions, Deficiencies, & Toxicities in Horses

  1. Pingback: Reverdy Adult Specific Energy Feed [REVIEW] ft. Cavalos | Tofino Tack

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