Calcium, Phosphorus, and other Macrominerals

Where is the majority of body calcium stored?

Approximately 99% is stored in bone and teeth.

What are the primary functions of calcium?

Bone/teeth structure, muscle contraction, nerve function, blood clotting

How does parathyroid hormone (PTH) respond to low blood calcium?

Increases bone resorption, decreases renal calcium loss, increase intestinal absorption.

What is the primary function of calcitonin regarding calcium?

stops bone resorption.

What causes nutritional secondary hyperparathyroidism?

Inadequate dietary calcium and/or an unfavorable calcium-to-phosphorus ratio.

What is rickets?

A disease in young animals characterized by defective bone mineralization.

What deficiencies commonly cause rickets?

Vitamin D deficiency, calcium deficiency, or phosphorus imbalance.

What are clinical signs of rickets?

Weak/bowed bones, enlarged joints, skeletal deformities, and poor growth.

What is milk fever in dairy cows?

Hypocalcemia (low calcium) occurring near parturition in high-producing dairy cows.

What is the standard emergency treatment for milk fever?

Intravenous calcium administration

How can milk fever be prevented prepartum?

Lower calcium intake so PTH is produced more

What are common feed sources of calcium?

Limestone, milk products, legumes/leafy forages, and animal byproducts.

What is the typical ideal dietary calcium to phosphorus ratio?

2:1

How does phosphorus distribution differ from calcium?

A larger proportion of phosphorus is found in soft tissues and metabolic compounds.

What essential biological structures require phosphorus?

ATP, nucleic acids, cell membranes, and bone.

What behavior in grazing cattle indicates severe phosphorus deficiency?

Pica (poor appetite and abnormal eating)

Why is dietary calcium deficiency largely preventable?

Calcium is easy and inexpensive to supplement, primarily using limestone.

What is phytate (phytic acid)?

The storage form of phosphorus in plants, poorly available to nonruminants.

What is the function of phytase in nonruminant diets?

An enzyme that breaks down phytate to release plant phosphorus.

What is the main inorganic calcium supplement?

Limestone (calcium carbonate).

What are common inorganic phosphorus supplements?

Dicalcium phosphate, monocalcium phosphate, and defluorinated phosphate.

What is the main intracellular cation?

Potassium (K+), maintained by the sodium-potassium pump.

What is the main extracellular cation?

Sodium (Na+), pumped out of cells by the sodium-potassium pump.

Why must sodium usually be added to livestock diets?

Plant feedstuffs are high in potassium but naturally low in sodium.

Why is potassium supplementation seldom needed under normal conditions?

Plants and common feedstuffs are naturally high in potassium.

What are the key physiological functions of chloride?

Acid-base balance, osmotic balance, and gastric hydrochloric acid (HCl) production.

Why can ruminants utilize inorganic sulfur supplements?

Rumen microbes use inorganic sulfur to synthesize sulfur-containing amino acids.

Why can't pigs and poultry utilize inorganic sulfur like ruminants?

They lack a rumen microbial system capable of synthesizing sulfur amino acids.

What is grass tetany?

A potentially fatal disorder caused by low magnesium availability on lush pastures.

How is grass tetany prevented in grazing cattle?

Supplementing magnesium, commonly via magnesium oxide or free-choice mineral mixes.

What are clinical signs of magnesium deficiency?

Hyperexcitability, muscle tremors, convulsions, grass tetany, and death.