Vitamins: Functions, Sources, Deficiency & Toxicity

• These notes cover key vitamins, their functions, sources, deficiency signs, and toxicity signs.

Vitamin A (Retinol)

• Function: Supports vision, epithelial tissue formation, nerve tissue development, and immune function.
• Sources: Beta-carotene (plants), retinyl palmitate (animal products), and synthetic sources.
• Deficiency Signs: Include night blindness, abnormal bone growth, epithelial atrophy, keratoconjunctivitis sicca, hyperkeratosis, and micro/anophthalmia.
• Toxicity Signs: Anorexia, weight loss, scaly dermatitis, bony exostoses, fractures, and death.

Vitamin D (1,25-dihydroxycholecalciferol)

• Function: Crucial for calcium absorption/reabsorption/resorption, bone health, and immune regulation.
• Sources: Sunlight (D3), fish, cod liver oil, egg yolk, fungi (D2), and synthetic forms.
• Deficiency Signs: Rickets in young animals, bone deformities, poor growth, and reduced egg production.
• Toxicity Signs: Renal failure, abnormal calcium deposits, and brittle bones and fractures.

Vitamin E

• Function: Acts as an antioxidant, supports immune function, and maintains reproductive organ integrity.
• Sources: Seeds, nuts, seed oils, and fresh forages.
• Deficiency Signs: Muscular dystrophy, stiffness, weakness, reproductive failure, white muscle disease in calves, mulberry heart disease in pigs, and yellow fat disease in cats.
• Toxicity Signs: Not Applicable.

Vitamin K

• Function: Essential for blood clotting; it is a cofactor for clotting factors II, VII, IX, and X.
• Sources: Green leafy forages, soybeans, fish meal, liver, and bacterial synthesis.
• Deficiency Signs: Prolonged clotting times and hemorrhage.
• Toxicity Signs: Not Applicable.

Vitamin C

• Function: Acts as an antioxidant and is involved in collagen synthesis and enzymatic reactions.
• Sources: Citrus fruits, green leafy vegetables, and synthesized from glucose in most animals.
• Deficiency Signs: Rare in most species, but can cause scurvy in susceptible species such as humans, primates, bats, fish, guinea pigs, and some birds.
• Toxicity Signs: Not Applicable.

Thiamine (B1)

• Function: Functions as a coenzyme in carbohydrate metabolism (TCA cycle).
• Sources: Cereal grains, beans, brewer's yeast, egg yolk, liver, kidney, and muscle meats.
• Deficiency Signs: Neurological dysfunction, weakness, anorexia, "beri-beri" in humans, cervical centroflexion in cats, and cerebrocortical necrosis in ruminants (can be caused by thiaminase).
• Toxicity Signs: Excess is excreted in urine and is, therefore, not toxic.

Niacin (B3)

• Function: Acts as a coenzyme in energy metabolism and DNA repair.
• Sources: Liver, yeast, meat, fish, poultry, and some synthesis from tryptophan (corn is a poor source).
• Deficiency Signs: Pellagra in humans (dermatitis, diarrhea, dementia, death), anorexia, feather abnormalities, and "black tongue" in dogs.
• Toxicity Signs: Bloody diarrhea, seizures, and death can occur.

Folic Acid (B9)

• Function: Critical for methylation reactions, DNA/RNA synthesis, cell growth, and red blood cell maturation.
• Sources: Green leafy plants, cereals, and oilseed meal.
• Deficiency Signs: Neural tube defects, anemia, poor growth, and cleft palate in puppies.
• Toxicity Signs: Excess is excreted in urine and is, therefore, not toxic.

Cyanocobalamin (B12)

• Function: Involved in DNA/RNA synthesis, energy metabolism, and hemoglobin production; must be bound to intrinsic factor for absorption.
• Sources: Animal origin foods (liver, meat) and bacterial fermentation.
• Deficiency Signs: Retarded growth, anemia, incoordination, weakness, decreased appetite, mortality, and dermatitis; often seen as a conditioned deficiency (e.g., EPI, IBD).
• Toxicity Signs: Not Applicable.