Vitamins are organic dietary essentials. They have diverse actions and are considered as vitamins on the basis of being required in small amounts. The term “vitamin” originated with Casmir Funk in 1912 while he was working with thiamine (vitamin B1), which is described as a “vital amine”. Subsequently, the term has been shortened and it is known that not all vitamins contain amine groups.ESSENTIAL VITAMINS FOR OUR BODY
The principle goal of vitamin prophylaxis and therapy is to provide a sufficient quantity of these metabolic essentials so that normal body functions can proceed. Plants and microbes normally synthesize vitamins or precursors. Subsequent utilization of the plant or microbe by domestic animals provides the vitamin to the host.
FAT SOLUBLE VITAMINS
Historically, a discussion
of vitamins, whether it is nutritional, Pharmacologic or biochemical, is based
on separating these micronutrients on the basis of their solubility
characteristics. Such a format will be followed here. Vitamin D is increasingly
considered a hormone because of it synthesize, storage, release, and activation
as needed; nevertheless, it will be discussed in this chapter. The four
fat-soluble vitamins are A, D, E and K.
VITAMIN A
Source and occurrence
Vitamin A is a generic term
for compounds possessing the biologic activity of retinol. Retinol is a term
used to designate natural forms of vitamin A and synesthetic analogs. Vitamin A
(retinol0 is an organic alcohol formed in animal tissue from various plant
carotenoids, a number of which have provitamin A activity. Vitamin A2
(dehydroretincl) is found in fish. The carotenoids vary in effectiveness as
precursors of vitamin A. It is not possible to absolutely equate plant
provitamin A activity with subsequent availability to the animal (Ullrey 1972).
In addition to differences in
effectiveness of carotenoid transformation to active vitamin, various species
have a considerable range of ability to use the provitamins that are present.
All green parts of plants have provitamin A activity; leaves have a higher
concentration than stems. Legume Hay is a richer source than grass hay.
Considerable provitamin activity is lost during harvesting, curing, and
storage. Provitamin A activity is close to zero within 6 months after harvest.
Dehydrated alfalfa remains one of the better natural sources, yellow corn is
the only concentrate containing significant amounts and cereal grains contain
negligible quantities. Animal fat products, particularly fish oils and liver,
contain large amounts of vitamin A. Polar bear livers contain such high
quantities that they are toxic if ingested by humans. Pure vitamin A is synthesized
commercially for supplementation and therapeutic use in medical practice.
The rate of observation of all
fat soluble vitamins is dependent on other lipid constituents in the diet and
on biliary and pancreatic secretions in the small intestine. Many carotenoids
are believed to be destroyed in the rumen.
Vitamin D
Source and occurence
vitamin D is the generic term for closely
related steroids that have antirachitic activity. They are formed as provitamins both plants and animals
and undergo initial conversion by ultraviolet light. Plant provitamin is ergocalciferol (vitamin D2). Green, growing plants contain only minute amounts. Most of the vitamin is formed in grass and hay from ergosterol during the curing process. It is in higher concentration in leaves than in stems. Ergocalciferol has little biologic activity in avian species but it is effective in mammals. This is apparently because of the more rapid excretion of vitamin D2,so that its biologic effect is minimized. Cholecalciferol (vitamin D3) is formed in animal
tissue by action of ultravoilet ray on 7-dehydrocholesterol, which is produced from cholesterol. The efficiency of conversion is dependent in several factors. Fair skin, light hair covering, nearness to the equator, and lack of cloud cover all promot conversion.The converse is also true in that animals with thick hair coats in northen latitude do not obtain sufficient vitamin D from their own bodies. If they are inside or there is heavy cloud cover, thus the deficiency intensified.
At one time, artificial irradiation of the
plants and animals sterols provided vitamin D activity. Today synthetic
cholecalciferol is used to supply additional vitamin D, a process that provides
more accurate fortification.
Vitamin E
Source and occurence
Vitamin E is the name given to a group of
biologically active tocopherols. The principal naturally occuring active
compound is d-∞-tocopherol.
Vitamin E is a widely distributed in plant products. It is abundant in whole
cerael grains and young, green leafy plants. Alfalfa, including cured hay is a good source.
Animals product are generally poor
sources of vitamin E. Plants oil have the highest content of natural products.
Synthetic sources are available. Certain legumes contain substances that
decrease vitamin E absorption.
VITAMIN K
Source and occurence
Vitamin K, a quinone, is a synthesized and
absorbed in sufficient amounts in the digestive tract of all species but
poultry. It is subsequently absorbed in the small intestine of ruminants and may be acquired by coprophagy or absorption from the lower intestinal tract in other mammals. Green leafy plants and cured roughage are excellent sources of vitamin K. Fish meal and liver contain significant amounts.
WATER SOLUBLE VITAMIN
The water soluble vitamins (B complex,vitamin C) are a functionally diverse group of micronutrients required by all animals.
Vitamin B1 (Thiamine)
Thiamine is the first of vitamin B complex to be isolated and purified. It is metabollic necessity for plants and animals. Thiamine is synthesized by plants and bacteria and has a ubiquitous distribution.
Niacin
Niacin, USP, or its active form, nicotinamide, is a metabolic essential for all animals but ia s dietary essential only under species conditons. In spite of this, niacin deficiency was a serious health problem for humans in the early part of this century. Dogs may experience niacin deficiency if fed improperly.
Biotin
A deficiency of biotin, INN, has been
considered a curiosity, since animals most receive an antivitamin avidin, to
develop a deficiency. Avidin is an albumin produced by the mucosa of the
oviduct. It can bind biotin and render it unavailable, Biotin deficiency has
been linked with the condition known as fatty liver and kidney syndrome, which
has been recognized in broiler chickens fed wheat has a major dietary
ingredient.
Choline
Choline is available aas coline
bitaratrite, NF, coline dihydrogen citrate, NF and coline cholride, INN.Choline
is in some ways anaglous to niacin. It can be formed and essential although
often limiting amino acid precursor, methionine. Simple stomachede on animals on
high grains rations may develop deficiencies.
Ribiflavin (B2)
pentethenic acid (B5)
pyrodoxin (B6)
folic acid (B9)
cynocobalamin (B12)
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