Goff/Duke's Chapter Questions (Minerals) Flashcards
You are called to examine a jersey cow that is unable to stand. Her newborn calf is beside her. What condition might this cow have? What role did the high potassium alfalfa hay fed to her the last days before calving play in the development of this disorder?
Milk fever;
High potassium diet alkalinizes her blood, interfering with PTH receptors on bone and kidney tissue.
As a result she has difficulty maintaining calcium homeostasis at the onset of lactation.
What role does high-potassium forage play in the lactating beef cow exhibiting signs of tetany?
In can reduce Mg absorption across the rumen resulting in hypomagnesemia.
Hypomagnesemia directly increases nervous system excitability and can also contribute to hypocalcemia.
Explain how a high-grain diet with no supplemental calcium added might affect the bones of a growing horse?
High-grain diets tend to be high in phosphorus.
When coupled with low dietary calcium there is an upset in the amount of calcium that can be absorbed and utilized for bone formation.
This stimulates excessive secretion of PTH, causing bone resorption.
The normal bone osteoid is often replaced by a fibrous collagen resulting in osteodystrophy.
If the matrix is not replaced, the result is osteoporosis.
On a very hot day a farmer notices that the pigs’ waterer is no longer working. He fixes it and the pigs all run to the trough to drink. 3 hours later you receive a call to examine the pigs. They are staggering around in circles and several have died. What is going on?
Suddenly giving water to pigs that are severely dehydrated causes water to move rapidly into the brain where salt concentrations are elevated due to dehydration.
Rapid rehydration results in brain edema and neurological dysfunction.
Why do cows with displaced abomasum have high blood pH?
The chloride excreted into the abomasum is not reaching the small intestine due to sequestration within the displaced abomasum.
Lack of chloride ions in the blood causes metabolic alkalosis.
Explain why a dog suffering from bilateral hypoadrenocorticism might develop hyperkalemia.
Lack of aldosterone production can reduce renal potassium excretion.
Your practice is located in an area where the soil is very rich in molybdenum. When you visit the herbivores in the area, what symptoms should you be alert for and why do these lesions develop?
Copper deficiency is suspected, causing a lack of pigmentation of the hair coat, poor growth and performance, and anemia.
Molybdenum and diet sulfur form a tetrathiomolybdate-copper complex that renders diet copper unavailable for absorption leading to copper deficiency.
A Bedlington terrier has just whelped (gave birth to puppies). Her owner reports that the dog is jaundiced and is urinating small amounts of dark urine. What is a likely diagnosis and why does this occur at whelping?
Copper toxicity.
The stress of whelping causes sudden release of large amounts of copper from the liver.
Free copper is such a strong oxidizing agent that it causes a hemolytic crisis.
The throat of a stillborn hairless lamb has a large mass. The ewe has spent the winter on a kale pasture. What happened?
The lamb developed goiter (hypothyroidism) = iodine deficiency.
Kale contains a goitrogenic substance interfering with iodine utilization by the mother’s thyroid gland.
She in turn strives to save herself by increasing uptake and storage of iodine, leaving none for the developing fetus.
What is mulberry heart disease?
Selenium deficiency of pigs causing changes in the muscle of the heart.
Pigs with scaly-looking skin and lots of itching with lesions and redness at the top of the foot are brought to your attention. Examination of the ration reveals that 4x as much calcium as is required is being put into the ration. What has happened to the pigs?
Excessive calcium in the diet has interfered with zinc absorption causing a zinc deficiency.
Zinc is critical to normal keratinization processes.
Why is metallothionein production in enterocytes important?
Metallothionein is produced by enterocytes in response to high zinc and to a lesser extent copper stores in the body.
It will bind any Zn or Cu that enters the enterocyte and sequester it within the cell until the cell sloughs off into the lumen.
The trapped mineral then passes out with the feces.
metallothionein is a critical factor for preventing Cu and Zn toxicity in many species.
