L3-Micronutrients

Characteristics of vitamins

• organic compounds (carbon skeleton)

• can be lipid or water soluble

• may or may not be considered ‘essential’ (depends on species)

Functions of vitamins

• metabolic regulation

• coenzymes

• antioxidants

Functions of Vitamin A

• Vision

• Growth

• Tissue maintenance

• Immune function

• Embryonic development

Forms of Vit A

Biologically active forms:

• Retinol

• Retinal (retinaldehyde)

• Retinoic acid

Storage (inactive) forms:

• Retinyl ester → from animal products (stored in liver)

• beta-carotene → (mostly) from plant products (red/orange pigmentation)

Rhodopsin and iodopsin=

Retinal+opsin (light sensitive protein)

Where is rhodopsin and purpose

• Photoreceptor found in rod cells of the retina

• Black and white vision

• Dim light vision (‘night vision’)

Where is iodopsin and purpose

• Photoreceptor found in cone cells of the retina

• Colour vision

• Bright light vision

Vitamin A toxicity

• Hypervitaminosis A

• Due to excess preformed Vit A (not beta-carotene

Vitamin A deficiencies

• fetal abnormalities

• impaired growth

• night blindness

Vitamin A (preformed) is essential for which animals

• felids

• marine birds

• most carnivorous mammals

*Lack sufficient quantities of 15,15’dioxygenase, which converts beta-carotene into retinal

Vitamin A (preformed) is not essential for which animals

• canids (e.g. foxes, coyotes, wolves)

• most herbivores

• most omnivores

*Readily convert beta-carotene to Vitamin A

Functions of Vitamin D

• Homeostatic regulation of calcium and phosphorus

• Growth

• Bone remodeling

• Eggshell formation

Sources of Vitamin D

D2 = ergocalciferol

• very few natural sources (foods often fortified with D2)

D3 = cholecalciferol

• sunlight (UV-B exposure), phytoplankton, zooplankton, marine fish

Active and Inactive forms of Vitamin D3

Inactive

• D2(diet)

• D3 (sunglight, diet)

Active

• Calcitrioll 1,25-dihydroxycholecalciferol, 1,25-dihydroxyvitamin D 3 or 1,25(OH)2D

Vitamin D3 synthesis steps

1. Ultraviolet B (UV-B) radiates the skin

2. UV-B initiates conversion of 7-dehydrocholesterol → Vit D3 (cholecalciferol)

3. Conversion of Vit D3 → 25-hydroxyvitamin D3 (calcidiol or 25(OH)D) in the liver

4. 25-hydroxyvitamin D3 → 1,25-hydroxyvitamin D3 (calcitriol or 1,25(OH) 2D) in the kidney

*This active form of VitD (calcitriol) is what regulates Ca/P

Which animals require Vitamin D

Only required in the diet for mammals with insufficient sun exposure

• Polar regions

• Fossorial/subterranean

• Nocturnal

Which animals is Vitamin D3 essential for

• amphibians

• birds

• reptiles

- Cannot use Vitamin D2

- Mammals can use D2 or D3

Vitamin D toxicity

• Hypervitaminosis D (hypercalcemia)

• Calcium builds up in soft tissues and organs (ex. muscle, organs, brain, tissue)

Vitamin D deficiency

• Rickets (soft bones, young animals)

• Osteomalacia (brittle bones, adults)

Vitamin E function

• Antioxidant

• Inhibits/prevents oxidative damage

• Scavenges free radicals (unstable/reactive atoms)

Vitamin E sources

1. Tocopherols (alpha, beta, gamma, delta)

• Organic compounds with various methylated phenols

• Alpha-tocopherol = most active form of Vitamin E

2. Tocotrienols (alpha, beta, gamma, delta)

Vitamin E toxicity

• hypervitaminosis E

• can counteract the actions of Vitamin K (blood coagulation)

Vitamin E deficiencies

• Muscular dystrophy (muscle weakness, paralysis)

• Nerve damage

• Infertility in rats and birds

Vitamin K function

Coagulation (blood clotting)

Vitamin K sources

K1 = phylloquinone

• Leaves of green plants

K2 = menaquinone

• Animal tissue and gut bacteria (both convert K1 → K2)

K3 = menadione

• Synthetic precursor

• Inactive in synthetic form

• Plants and bacteria can activate it (animals cannot)

Vitamin K toxicity

• K1 and K2 are innocuous (harmless), even in very large amounts

• K3 can be toxic (not used as a supplement anymore)

Vitamin K deficiencies

Risk of hemorrhage or excessive bleeding

Types of B vitamins

• B1- thiamine

• B2- riboflavin

• B3- niacin (nictonic acid & nicotinamide)

• B5- pantothenic acid

• B6- pyridoxine & pyridoxamine

• B7- biotin

• B9- folate/folic acid

• B12- cobalamin

Thiamine function and deficiency

Function: Coenzyme/precursor for cell metabolism

Deficiency: Beriberi → edema, heart problems

Riboflavin function and deficiency

Function: Coenzyme/precursor for cell metabolism

Deficiency: Ariboflavinosis → skin disorders, edema

Niacin(nicotinic acid) and Nictoinamide function and deficiency

Function: Coenzyme/precursor for cell metabolism; can be synthesized from tryptophan (poor efficiency)

Deficiency: Pellagra → skin disorders, dementia, diarrhea

Pantothenic Acid function and deficiency

Function: Precursor for Coenzyme A → critical for TCAC

Deficiency: Rare

Pyridoxine & Pyridoxamine function and deficiency

Function: Amino acid metabolism; higher requirement in carnivores

Deficiency: Dermatitis

Biotin function and deficiency

Function: Coenzyme/precursor for cell metabolism; can be synthesized by gut bacteria so may not be essential for ruminants

Deficiency: Anemia + hair loss

Folate/folic acid function and deficiency

Function: Coenzyme/precursor for cell metabolism; can be synthesized by gut bacteria so may not be essential for ruminants

Deficiency: Folate-deficiency anemia

Cobalamin

Function: Coenzyme/precursor for cell metabolism; synthesized by gut bacteria so all animals depend on microbially synthesized B12

Deficiency: Severe + irreversible brain and CNS damage

Vitamin C (ascorbic acid) functions

• Antioxidant

• Collagen formation

• Hormone synthesis

• Absorption of iron

Vitamin C deficiencies

Scurvy (skin disorders, impaired wound healing, risk of hemorrhage)

Who is Vitamin C essential and not essential to?

Vitamin C synthesis

Choline and Inositol functions

• Structure of cellular membranes (both); Phosphatidyl-Inositol & Phosphatidylcholine

• Lipid transport and metabolism (Choline)

• Neurotransmitter synthesis (Inositol)

Characteristics of Choline and Inositol

Choline (‘Vitamin B4 ’)

• conditionally essential

• Synthesized from methionine*

Inositol (‘Vitamin B8 ’)

• non-essential

• Synthesized from glucose*

*Synthesis is slow (potentially insufficient) during growth and geriatric phases

Characteristics of minerals

• Inorganic compounds (no carbon skeleton)

• All are essential (cannot be synthesized by any animal or plant)

How can minerals be obtained in diet

• From plants (who accumulate minerals from the soil)

• From animals (who accumulate minerals from eating plants/animals)

• From free water

Thus environment has large influence on mineral availability

Types of macro & microminerals

* Although these are the main trace minerals, there are more than a dozen which can be found in the body including: arsenic, nickel, silicon, and boron

** ruminants only

Function of minerals

1. Part of skeletal structures; e.g. calcium & phosphorus in bone

2. Maintenance of osmotic pressure; e.g. sodium in extracellular fluid/potassium in intracellular fluid

3. Regulation of acid/base balance; e.g. chloride in the kidneys

4. Components of enzymes; e.g. cobalt as part of vitamin B12

5. Activators of enzymes; e.g. calcium activates enzyme CaMKII

6. Components of biological units; e.g. hemoglobin contains iron and thyroxine contains iodine

Organic vs Inorganic Minerals

Nutritionally Organic Minerals

• Minerals which are chelated (bound) to a carbon containing compound (e.g. amino acid)

• Generally, more bioavailable

Nutritionally Inorganic Minerals

• Elements or molecules without carbon

• Generally, less bioavailable

Two most abundant minerals in the body are:

Calcium and Phosphorus

Calcium function and where it’s found

• formation of bone/teeth/antler/eggshell/milk (main role)

• found in milk, eggs, bone, vegetation

Phosphorus function and where it’s found

• formation of bone/ATP/phospholipids (main role)

• found in animal tissue, milk, grains*, vegetation*

*In plants, much of the P may be present as phytate

Calcium/Phosphorus deficiency and requirements

• Rickets (young animals) or osteomalacia (metabolic bone disease)

• Requirement = considered as a ratio (Ca:P should be 1:1 – 2:1)

Electrolytes and examples

intracellular/extracellular fluid balance

ex.

Cations: Ca2+, Mg2+, Na+, K+

Anions: P(PO43-), Cl-

Electrolytes function

Create osmotic gradients to regulate body fluid status/movement

Electrolyte imbalance results in

• cardiovascular issues (chronic)

• fatigue and emesis (acute)

Who is cobalt essential to

Only essential mineral for ruminants (foregut fermenting species) and some monogastric hindgut fermenting species

Cobalt function

Synthesis of Vitamin B12 (cobalamin)