Vitamins Flashcards
What are vitamins?
Vitamins are organic compounds distinct from fats, carbohydrates, and proteins.
They are natural components of foods where it is usally present in minute amounts.
Vitamins are essential for normal physiological function (ex. maintenance, growth, development, etc.)
Would vitamins be found in proximal analysis?
No, because all organic material is burned off
Why are vitamins essential?
They are not synthesized by the animal in amounts adequate to meet normal physiological needs.
Absence of vitamins in the diet or their under-utilization can cause a specific deficiency syndromes.
Describe some caveats related to vitamins.
Some compounds are vitamins for one species and not for another. (ex. Vitamin C and choline)
Some compounds are vitamins only under specific dietary or environmental conditions. (ex. Vitamin D and niacin)
What is a vitamer?
Vitamers are different chemical compounds that show the same biological activity.
i.e. different structures but act as the same vitamin
What are pro-vitamins?
Compounds that can be metabolized to yield a vitamin (ex. some carotenoids to Vitamin A).
They do not have vitamin activity by itself but can become a vitamin in the body.
Why are vitamins generally important in terms of their overall function?
Vitamins act as coenzymes that aid in enzymatic reactions.
What is a coenzyme?
A small, organic non-protein molecule that carries chemical groups between enzymes.
In general, vitamins act as coenzymes
What is a cofactor?
A non-protein, chemical element that is bound tightly to an enzyme and it required for catalysis.
In general, minerals act as co-factors
Describe how some vitamins function as antioxidants.
Antioxidants are molecules that disrupt oxidation via free radicals. They themselves are easily oxidized by the free radicals in place of other molecules. Vitamins that are oxidized are destroyed, so it is important to keep them at appropriate levels.
Some examples of antioxidant vitamins are E and C.
What are the fat soluble vitamins?
A, D, E, K
They are stored in the liver or in adipose tissue
What are the water soluble vitamins?
B and C
They are not stored in the body and must be provided regularly
Describe the vitamers of Vitamin A
- Retinal: aldehyde form
- Retinol: alcohol form
- Retinoic acid: acidic form
- Retinyl esters: esters of all-trans retinol
What is the active form of Vitamin A?
Retinol
What is beta-carotene and how is it related to Vitamin A?
Beta-carotene is a pro-vitamin that is converted to Vitamin A in the body. (not in cats)
Describe the relationship between beta-carotene, Vitamin A, and milk fat.
There is an inverse relationship between Vitamin A and milk fat synthesis.
There is a positive relationship between beta carotene levels and milk fat percentage.
Efficiency of converting beta carotene to Vitamin A varies by and within species.
For example, Holsteins convert beta carotene to Vitamin A efficiently, and have more Vitamin A in circulation. Therefore, they have lower milk fat.
In contrast, Jerseys are less efficient at converting beta carotene to Vitamin A, so they have a higher milk fat percentage.
Describe the cat’s interactions with Vitamin A.
The cat is NOT ABLE to convert beta carotene to active vitamin A. Sources of vitamin A are required in the diet.
Cats are obligate carnivores that have not evolved the mechanism to convert beta carotene to Vitamin A.
What are some chemical properties of Vitamin A?
- good reducing agent
- forms of vitamin A are soluble in organic solvents and insoluble in water
- unstable in the presence of oxygen and acids
- it is oxidized over time, so when feeding stored forages, we supplement them with vitamin A to meet requirements (Vitamin A activity decreases the longer a forage is stored)
What are international units?
Standardized measure of biological activity or effect of a compound based on utilization of various forms of vitamin A by rats.
What are the general functions of Vitamin A?
- vision
- maintenance of mucous membranes
- glycoprotein synthesis
- reproduction
- growth
- corticosterone synthesis
- immune function
How is vitamin A associated with vision?
It is involved in the production of rhodopsin, the pigment used in low light.
Retinal (active form/vitamer) joins opsin to form rhodopsin. This helps the eye distinguish between light and dark changes. Conformational changes in the protein cause a nerve impulse to the brain.
How is Vitamin A associated with mucous membranes?
In maintains the epithelial linings of the soft tissues around the eye, digestive tract, respiratory tract, urogenital tract, and the corneal epithelium.
What is the relationship between Vitamin A and glycoproteins?
Vit. A helps synthesize glycoproteins, like mucins, which protects epithelial linings.
How is Vitamin A involved in reproduction?
Vitamin A is required for reproductive function in both males and females.
It is involved with the hatchability of eggs, neonatal development, and spermatogenesis.
How is Vitamin A related to growth?
It is required for growth and differentiation of cells. Proper bone growth is also associated with Vit. A.
How is Vitamin A associated with the synthesis of corticosterones?
Lack of Vitamin A causes atrophy of the adrenal glands; its needed for production of cortisol and adrenalin.
How is Vitamin A related to immune function?
Vitamin A helps produce the mucin and maintain the linings involved in immune response. Therefore, deficiency leads to a reduced immune response.
How is Vitamin A involved in such diverse functions?
It plays a key role in certain aspects of gene transcription. As a result, Vitamin A has the most functions.
How and where is vitamin A stored?
In the liver and adipose.
Cattle can store a 6-month supply when 1 million IU are given via injection. This is done for cattle on winter range.
What are some animal sources of Vitamin A?
cod liver oil, liver, egg yolk, butter
What are some natural or plant sources of Vitamin A?
carrots, kale, sweet potatoes, pumpkins, spinach (all high in beta carotene)
What are some deficiency symptoms of Vitamin A?
- night blindness
- xerophthalmia (inability to produce tears, dryness of the conjunctiva and cornea)
- keratinization of respiratory epithelium
- death
What foods are low in vitamin A activity?
Grains
Yellow corn is the only grain with “significant” Vit. A activity
What is hypervitaminosis A?
ingestion of a large excess of vitamin A
Vit. A is one of the few vitamins that can be toxic
What are gross toxicity signs for Vitamin A?
- roughened hair coat
- scaly skin
- hyper irritability and sensitivity to touch
- blood in urine and feces
- loss of control of legs and inability to rise
- periodic trimmers
Describe vitamin A toxicosis in cats
- most often reported in cats that have been fed diets composed exclusively of liver and other organ meats
- syndrome called deforming cervical spondylosis
- causes bony exostoses (outgrowths) to develop along the muscular insertions of cervical vertebrae and the long bonds of the forelimbs
Discuss the first observed instance of Hypervitaminosis A in humans.
In 1913, Arctic explorers lost their rations and resorted to eating wild animals like seals and other high fat animals. The members of the expedition exhibited fatigue, abdominal pain, bone and joint pain, and insomnia. Only one member survived the trip back to their base.
What are some sources of Vitamin D?
- exposure to sunlight/UV is a factor that contributes to the formation of Vitamin D
- most foods contain a small amount of vit D.
- fortification of vit. D in food has become widespread
What are the two forms of vitamin D?
ergocalciferol (D2) and cholecalciferol (D3)
these are vitamers
What is the plant form of Vitamin D?
ergocalciferol (D2)
What is the animal form of Vitamin D?
cholecalciferol (D3)
Describe Vitamin D metabolism in animals starting with exposure to sunlight.
Sunlight stimulates conversion of 7-dehydrocholesterol to Vitamin D3, which goes to the liver. It is then converted to 25-hydroxyvitamin D3. Next, it goes to the kidneys and is converted to the active form 1,25-dihydroxyvitamin D3. (aka 1,25 (OH)2D3)
What is the active form of Vitamin D called?
1,25 (OH)2 D3
What are some functions of the active form of Vitamin D in the intestines?
Induces synthesis of calcium binding protein (required for uptake of calcium from intestinal lumen); stimulates transport of phosphorous and magnesium
What is the active form of Vitamin A?
Retinol
How does active Vitamin D function in bone?
It causes mobilization of calcium.
It binds to receptors and appears in the nuclei of osteoblasts and osteocytes, mobilizing the uptake or release of calcium
How does active vitamin D function in the kidneys?
It is involved in calcium conservation and increases phosphorous reabsorption.
What are some natural sources of Vitamin D?
Cod liver oil, beef liver, sun-cured alfalfa, egg yolk, UV irradiated mushrooms
Describe the relationship poultry have with Vitamin D
In all species except for poultry, Vitamin D2 is equal to D3. Poultry require a preformed D3.
Describe the relationship dogs have with Vitamin D
Dogs do not absorb sunlight, and so they need a dietary supplementation of Vitamin D. They can use both D2 and D3.
How is Vitamin D stored?
It is stored in the liver and can be stored for a max of three months.
It can be produced by the animal, but housing conditions and hair coats are complicating factors.
Winter range cattle can get an injection.
Arctic animals get Vitamin D through their diet.
What animals absorb Vitamin D better from sunlight?
Adult animals and lighter skinned animals are better at absorbing sunlight and producing Vitamin D
What are some general effects of Vitamin D deficiency?
- causes a disturbance in the absorption of calcium and phosphorous
- results in insufficient bone calcification
- in swine: it takes 4 to 6 months for pigs fed a Vitamin D deficient diet to develop signs of deficiency
What is rickets?
Rickets is the development of soft bones in young animals due to Vitamin D deficiency
What is osteomalacia?
This is a disease in adult animals resulting from Vitamin D deficiency where there is decreased mineral content and softening of the bones
What are some subclinical signs of Vitamin D deficiency?
Reduced growth, milk production, egg production, and reproductive performance
- Lack of bone calcification and proliferation of ephyseal cartilage
- rib and vertebra fractures
- low plasma calcium, magnesium, and inorganic phosphorous levels
- elevated serum alkaline phosphatases
What does a primary deficiency in Vitamin D cause?
A secondary deficiency in calcium and phosphorous
What is the most toxic Vitamin?
Vitamin D
can be used as rat poison for this reason
How does Vitamin D toxicity usually occur?
Formulation errors
What are some symptoms or effects of Vitamin D toxicity?
- reduced feed intake (anorexia)
- reduced growth rate
- reduced liver weight
- excess calcium in blood (hypercalcemia)
- reduced weights of the radius and ulna
- calcification of the aorta, heart, kidney, and lung
- dehydration, vomiting, fatigue
What are the vitamers of Vitamin E?
tocopherol and tocotrienol
How was Vitamin E discovered?
Discovered in 1936 as a dietary fertility factor in rats
How does Vitamin E appear in its pure form?
light yellow oils
What are the differences between tocopherols and tocotrienols?
Tocopherol has no double bonds
Tocotrienol has double bonds
Both are vitamers of vitamin E
How can the vitamers/chemical forms of Vitamin E exist?
can exist in alpha, beta, gamma, or delta configurations
What is the most common chemical form of Vitamin E?
alpha-tocopherol
(synthetic dl-form)
What are some sources of Vitamin E?
cereal grains, vegetable oils, wheat germ oil, animal fat, alfalfa
What the intake of Vitamin E affected by?
affected by intake of:
- selenium
- unsaturated fatty acids
- antioxidants
- and by tissue reserves
These factors can cause secondary deficiencies
Describe the relationship Vitamin E has with selenium
Vitamin E has a selenium sparing effect, meaning it can fill in for selenium in metabolic pathways if it is deficient.
What are some chemical properties of Vitamin E?
- it’s an antioxidant (easily oxidized in presence of minerals and PUFA)
If oils are high in Vitamin E, why should we include a synthetic antioxidant?
Included because we don’t want all of the Vitamin E to be oxidized if we are trying to ensure high Vit. E activity
What are some functions of Vitamin E?
Its main function is as an antioxidant
- protects Vitamin A
- prevents oxidation of PUFA
- interrelated with selenium
Vitamin E also protects cell and mitochondrial membranes
What are muscular symptoms of Vitamin E deficiency? Examples of diseases?
Nutritional muscular dystrophy (or cardiomyopathy)
1. Mulberry heart disease (pig)
2. Stiff lamb disease
3. White muscle disease (calves)
4. Degeneration of nerve cells (poultry)
What effect does Vitamin E deficiency have on red blood cells?
Hemolysis of red blood cells
What effect does Vitamin E deficiency have on the reproductive system?
Males: inhibition of spermatogenesis
Females: fetal resorption (degeneration)
What disease results in cats from Vitamin E deficiency?
Pansteatitis - aka yellow fat disease