horse and pig final part 2 (lec 23-24, and first part)

Why do fat-soluble vitamins require the presence of dietary fat and bile for absorption?

• fat-soluble vitamins require dietary fat and bile for absorption because they are fat soluble so it impacts their absorption, transport, and storage

• they need bile acids and dietary fat for micelle formation and absorption across the intestinal wall

which two fat-soluble vitamins act as coenzymes

• vitamin A (retinal or retinaldehyde) + vitamin K (phylloquinone and menaquinone) - coenzymes during specific biochemical reactions such as:

  • light perception for vision

  • Ca binding during coagulation reaction and bone formation

what is most common storage form of vitamin A in animal tissues

• Retinyl palmitate is common stored form of vitamin A esterfied to fatty acid palmitate

• Primary storage form in animal tissues, especially liver

What is difference between beta-carotene and retinol

Beta-carotene (provitamin A carotenoid) is inactive and found in plants → can be converted to retinol (active form of vitamin A) by animals using 15,15-dioxygenase found in small intestine and liver.

How do pig and horses obtain vit A from plant diet

from beta carotene from plants, forage, or carrots → convert to retinol using intestinal enzymes 15,15-dioxygenase from small intestine/liver

What is the source of vitamin D2 and what organisms produce it

Vitamin D2, ergocalciferol, is from fungus (mold/yeast) in plants(forage) → ergosterol UV exposure when leaves are exposed to the sun after harvest converts to Vitamin D2

what is the precursor of vitamin D3 in animals?

7-dehydrocholesterol (on animal skin) is a precursor for vitamin D3 → converted via UV light to vitamin D3

name 2 natural sources of vitamin E

• Plant oils - mostly leaves have alpha-tocopherol

• In animal products, vitamin E is present as tocopherol esters such as tocopherol palmitate found in found in fatty fish (salmon, trout, cod), certain seafoods, snails, liver, animal fat

What is the significance of the acetate form of alpha-tocopherol in supplements?

Acetate form (alpha-tocopheryl acetate) is synthetic and more stable for feed use, and more oxidation resistant compared to natural vitamin E sources that are unstable.

What does "all-rac" alpha-tocopheryl acetate refer to?

all-rac means full racemic mix of D and L isomeric forms of alpha tocopherol in synthetical vitamin E supplements.

D and L tocopheryl acetate!

What are the two major forms of vitamin K, and where is each typically found?

• vitamin K1 (phylloquinone) found in green leafy plants

• vitamin K2 (menaquinone) from animal products and bacteria microbial synthesis

Which vitamin E form is most biologically active?

alpha tocopherol. most bioactive and abundant in animal tissues

What is the structural feature that defines the vitamin K group?

Methylated naphthoquinone ring with a hydrocarbon side chain that is an isoprenoid

Why would vitamin D2 be variable in harvested forage?

if bad quality forage → then source of D2 is often not sufficient

A horse is kept indoors during the winter. What fat-soluble vitamin might be deficient and why?

• Horse indoors during winter -> vitamin D3 deficiency bc limited UV exposure so reduced cutaneous synthesis of vitamin D3. 

• May need supplementation in the feed or forage

Which vitamin may be deficient in hay stored over 6 to 12 months?

Vitamin E deficient because hay depletes after 6 months

How might reduced bile secretion affect the absorption of all four fat-soluble vitamins?

• Bile secretion is important for fat-soluble vitamins because fat soluble vitamins bind to bile + dietary fat -> into micelle to be absorbed across intestinal wall.

• If bile secretion is reduced -> decrease absorption of fat-soluble vitamins -> vitamin deficiencies