VITAMINS LECTURE 12

VITAMINS What Affects Requirements? Age Stage of Production Variety of stresses including: Gastrointestinal Infections Intense Muscular Exercise

VITAMINS Need for supplemental vitamins depends on what? Type and quality of diet Amount of microbial vitamin synthesis in the digestive tract Extent of vitamin absorption from the site of synthesis Horses grazing high-quality pastures Need little or none Forages are a rich source of most Fat and water-soluble vitamins

FAT-SOLUBLE VITAMINS A, D, E, and K Generally expressed in International Units (IU) Diseases that interfere with fat absorption also Affect these vitamins Mineral oil may also affect undesirable losses

VITAMIN A β-carotene Biologically active molecule Important for: Vision Epithelial cell development Bone remodeling in the growing horse Highest concentrations found in: Green forage and yellow corn

VITAMIN A Carotenes slowly destroyed by: Light and heat Therefore, sun-cured hay is lower than fresh forage Stored hay gradually Declines in carotene concentrations Pasture provides tremendous more carotenes than U.S. #1 hay Conversion of carotene to Vitamin A occurs in Small Intestine

VITAMIN A Requirements are uncertain Good quality pasture and/or hay should Meet requirements Deficiencies include: Night blindness Hyperkeratinization of the cornea and skin Anorexia Poor growth Respiratory infections

VITAMIN D Two primary active compounds found in nature: D 2 (ergocalciferol) Result of ultraviolet irradiation of ergosterol Synthesized by plants Only found after they have been cut and exposed to sunlight D 3 (cholecalciferol) Result from the UV irradiation of 7-dehydrocholesterol Synthesized by the tissues of the horse Present in the skin

VITAMIN D Maintains calcium homeostasis Requirements have not been established Deficiencies unlikely Supplements have shown to ↑ Ca and P absorption Excesses can cause: Calcification of blood vessels Bone abnormalities and soft tissue calcification

VITAMIN E Generic Descriptor for α-tocopherol ~ 8 found in nature α-tocopherol most biologically active in horse Interrelationship with: Selenium – glutathione peroxidase Helps to prevent myopathies Located primarily in the lipophilic parts of the cell: All have high concentrations of glutathione peroxidase

VITAMIN E Grinding and storage of grains decreases E Exercise may increase requirements Difficult to determine deficiency differences between E and Selenium Signs of toxicity have not been produced

VITAMIN K Compound found in plants is K 1 or phylloquinone Bacteria are able to synthesize in the hindgut Ca ion and K interactions aid in blood clotting Requirements not determined Deficiency could lead to hemorrhage Toxicity has not been seen

WATER SOLUBLE VITAMINS B vitamins, except B 12 are usually Supplied in adequate amounts in good-quality forage Microbial synthesis of B 12 can Typically meet the nutritional needs Synthesis of other B vitamins Also takes place Mare’s milk provides necessary B vitamins to the foal

THIAMIN Synthesized in the S.I., cecum, and L.I. May still require dietary thiamin Important in metabolism Some plants as well as Coccidostats (amprolium) may tie up thiamin Requirements range from 3 to 5 ppm Deficiencies would include anorexia and loss of weight Toxicity is unlikely Research has indicated may create a calming effect

RIBOFLAVIN Synthesis in S.I., cecum, and L.I. Requirements ~2ppm Invovled: ATP synthesis Drug metabolism Lipid metabolism Antioxidant defense mechanisms No reports of deficiencies or toxicities

NIACIN Generic term for: Nicotinic Acid Nicotinamide Thought to be synthesized by tryptophan Also synthesized in G.I. tract No requirements have been established No deficiencies or toxicities have been reported

PANTOTHENIC ACID Also synthesized in G.I. tract No dietary requirements No deficiencies or excesses have been reported

VITAMIN B 6 Generic term for: Pyridoxine Pyridoxal Pyridoxamine Synthesized in the G.I. tract No dietary requirements No deficiencies or excesses reported

BIOTIN Synthesized in G. I. Tract No dietary requirements Reports of improved hoof health When fed 10 to 30 mg/d Deficiencies may lead to Poor hooves No excess levels reported

FOLACIN Generic term for Folic Acid Synthesized in G.I. tract Deficiencies and excesses have not described

B 12 Cyanocobalamin Synthesis with presence of Cobalt by microflora Deficiency has not been described

ASCORBIC ACID Also known as Vitamin C Thought to be synthesized from glucose In the body of the horse No reports of deficiencies or excesses