Phosphorus

Where is phosphorus at in the body (compared to Ca)?

About 80% of P is in the bone but much higher proportion than Ca in soft tissue

How is phosphorus level in the blood controlled?

Controlled by the parathyroid hormone (PTH), which increases blood calcium, lowers blood phosphate

What are the important signs of P deficiency?

• Rickets

• Pica (depraved appetite)

• Low blood serum levels

• Stiff joints/muscular weakness

• Decreased appetite

• Low weight gains

• Low milk production

• Low fertility

What factors affect Ca and phosphorus absorption?

• PTH

• Calcitonin

How are Ca and P excreted from the body?

Ca

• Excreted via feces

P

• Excreted in feces by herbivores

• Excreted in urine by carnivores

What feeds are fairly rich in P? What is the problem with most feed P?

• Milk, cereal grains, meat, and fish products are fairly rich

• Problem with most feed: forages tend to be low and variable

What can be done to increase P availability?

Use supplements

What are the main inorganic P and Ca supplements?

P and Ca salts

Phytic Acid

• Prevents absorption of minerals (binds to them instead) into the body

• In this case, decreases the body’s absorption of Ca and P

Phytase

Improves absorption (works against phytic acid)