Lecture 17 Vitamins (PDF)

Vitamins § Discovery and Isolation – 1912 § Association of diseases with dietary deficiencies dates back many many years: § Beriberi – (201 -300 AD) Ruminants Polioencephalomalacia  Kinderklinic in Vienna The veranda of the Meidling Hospital in Vienna with i...

Vitamins § Discovery and Isolation – 1912 § Association of diseases with dietary deficiencies dates back many many years: § Beriberi – (201 -300 AD) Ruminants Polioencephalomalacia  Kinderklinic in Vienna The veranda of the Meidling Hospital in Vienna with infants ‘receiving outdoor treatment in sun and shade respectively’ (MRC 1923: reproduced with permission § Rickets – 110 A.D. Rickets before the discovery of vitamin D O’Riordan & Bijvoet, 2014. BoneKEy Reports,3 Article number: 478 doi:10.1038/bonekey.2013.212  §Scurvy (1753) – “Sailors Disease” Symptoms of avitaminosis: Scurvy: the structure of collagen is defective Functions: spongy gums, bleeding from mucous membranes. Antioxidant synthesis of collagen synthesis of carnitine (aids fatty acid entry into mitochondria) biosynthesis of norepinephrine.  Rickets before the discovery of vitamin D O’Riordan & Bijvoet, 2014. BoneKEy Reports,3 Article number: 478 doi:10.1038/bonekey.2013.212 A copy of the Bill of Mortality for 1634 listing the number of deaths for each of the 122 parishes of the City of London. The causes of death are listed alphabetically and rickets is included among those on the right side. Reproduced with permission of The Guildhall Library of The City of London, London, UK.  Organic compounds required in small amounts. “Vitamines” – “accessory factors” thought to contain amino N “vital amine.” Cofactors in metabolic reactions. Donor or Acceptor groups for metabolic intermediates. Enzyme precursors, coenzymes, antioxidants. Some synthesized by microbes (pre- post-gastric fermenters?) Vitamin Classifications  Discovered in 1922 as a “fat-soluble factor” present in butter and fish oil. Includes several related compounds. Retinol is the biologically active form of Vit A. Functions of Vision. Bone growth. Vit A Reproduction –spermatogenesis and estrus cycles. Maintenance of epithelial cells Antioxidant Hypervitaminoses – varies with species, age and physiological condition. Results in skeletal abnormalities and thickening of skin. Vitamin D Sterol compound. Regulates Ca and P metabolism. Formed by irradiation of sterols in plants and skin.  Sun-cured forages and hay good sources. Confined animals require Vit D. Vit D3 needed for carnivores and omnivores Most animals D2 is converted to D3 - efficiency in poultry is very low. Regulates Ca and P metabolism. Formed by irradiation of sterols in plants and skin.  Vit D can be synthesized from cholesterol Steroid hormone activity Regulates DNA transcription in microvilli Synthesis of RNA – responsible for Ca-binding Cats: protein do not make vit D included in diet 7-dehydrocholesterol is converted to cholesterol Vitamin E Group of compounds called tocopherols & tocotrienols. ɑ- tocopherol most active biological form added to diets.  Functions of Vitamin E Antioxidant to protect cells from oxidative damage induced by free radicals. Prevents oxidation of lipids by serving as free radical scavenger – donates electrons from hydroxyl group (antioxidant effect). Lipid peroxidation causes damage to unsaturated lipids in cell membranes resulting in the disruption of the structural membrane and cell integrity. Peroxidation can reduce palatability and animal health. Protects proteins and Vit A. Deficiency of Vitamin E § White muscle disease (degeneration of heart muscle) § Exudative diathesis in chickens (leaky capillaries in breast muscle). § Encephalomalacia (crazy chick disease). Toxicity of Vitamin E § Least toxic of the fat-soluble vitamins. § High levels are added in diets of animals (beef, poultry, dairy) to enhance food nutritional value and lipid stability. Vitamin K § Includes a group of compounds called quinones. § Vit K1 found in plants (phylloquinones). § Vit K2 synthesized by microbes (menaquinones). § Menaquinone is the metabolically active form. § Vit K3 , menadione, most common synthetic form included in animal diets. § Liver converts K1 and K3 to K2  Synthesis of prothrombin, blood-clotting protein. Deficiency leads to hemorrhage Functions of or prolonged bleeding. Vitamin K Reduction in carcass quality or condemnation. GI tract microbes a good source of Vit K – absorption or coprophagy. Mold growth on sweet clover hay or silage contains dicoumarol, similar to Vit K in structure, and competitive inhibitor.  Water Soluble Vitamins B1 Thiamine B2 Riboflavin B3 Nicotinamide B5 Pantothenic acid B complex B6 Pyridoxine “Cow Manure Factor” B7 Biotin “Animal Protein Factor” B9 Folic acid ONLY from B12 Cyanocobalamin microbial synthesis Vit C --- Ascorbic acid Water No provitamins. Responsible primarily in energy Soluble transfer. Vitamins Absorbed more easily and readily from SI. Water soluble vitamins are not stored to a great extent. Excretion occurs both in feces and urine Rumen microbes can synthesize all. The equivalents of 1 IU for selected vitamins Vitamin A: 1 IU is the biological equivalent of 0.3 μg retinol, or of 0.6 μg beta-carotene. Vitamin D: 1 IU is the biological equivalent of 0.025 μg cholecalciferol or ergocalciferol. Vitamin E: 1 IU is the biological equivalent of 0.67 mg d-alpha-tocopherol, or 0.9 mg of dl- alpha-tocopherol.  Vitamin Content Varies § Concentrates – B vitamins § Forages – carotene Fresh grass ~250 mg/kg Ensiled grass ~125 mg/kg Artificially dried ~ 95 mg/kg Lucerne Hay has ~15mg/kg § Animal products – rich in most vitamins including lipid soluble but deficient in Vit C. § Microbial Fermentation Supplies Vit B12, K and Biotin Need other vitamins in diet