Hypocalcemia, Hypomagnesemia, DCAD

Question 1

Maintenance requirement for calcium

Answer 1

13g

Question 2

T/F: Ca demand increases dramatically at the start of lactation

Answer 2

True

Which sucks b/c dry matter intake is down so def not getting it from the diet

Question 3

If a cow is unable to take calcium in through her diet, where is she gonna try and get it from?

Answer 3

Plasma pool, extra cellular fluid, bone

Question 4

What are the three ways the cow can control Ca?

Answer 4

• SI: when Ca is low, Ca binding protein is stimulated by vitamin D to increase absorption
• Bone: PTH promotes resorption by osteoclasts in bone
• Kidney: PTH promotes conservation

Question 5

T/F: Hypocalcemia at parturition is attributable to PTH deficiency

Answer 5

False - Cows actually have higher concentrations of PTH

Question 6

T/F: Milk fever occurs most commonly within 24h after calving

Answer 6

True

Question 7

EARLY clinical signs of milk fever

Answer 7

Mild excitement, tetany, tachycardia, hyperthermia

Question 8

Classic clinical signs of milk fever

Answer 8

Sternal recumbency, depression
Flaccid paralysis
Tachycardia
Hypothermia
Atonic rumen, bloat, constipation
Dilated, unresponsive pupils

Question 9

LATE clinical signs of milk fever

Answer 9

Comatose
75% die w/o treatment

Question 10

What should a normal fresh cow’s calcium levels be?

Answer 10

> 8mg/dL

Question 11

What other clinical pathology changes might we see in a cow with milk fever?

Answer 11

Hypophosphatemia
Hypermagnesemia
Hyperglycemia - steroid influence

Question 12

Milk fever treatment

Answer 12

8-12g calcium IV SLOWLY and monitor HR
Usually 500mL of a 23% Ca gluconate solution

Question 13

How can we prevent milk fever?

Answer 13

• Maintain appetite and intake around parturition
• Avoid high K diets in dry period (thought to inhibit absorption of Ca)
• CaCl drench/tube at calving

Question 14

Creeper cows are

Answer 14

Hypophosphatemic

Question 15

T/F: to treat hypophosphatemia you should give 1-2 500mL bottles of CMPK

Answer 15

False - CMPK contains phosphite which won’t increase plasma P

Need to give phosphate - fleet enema IV or oral NA phosphate/dical phosphate

Question 16

Where is most magnesium absorbed?

Answer 16

Rumen and LI

Question 17

A cow has no endocrine regulation of Mg, meaning if they are low, they have no way of mobilizing magnesium from within the body. Where must cows get most of their magnesium?

Answer 17

Rely on daily intake
Diet usually meets requirements

Question 18

What are the two kinds of hypomagnesemia?

Answer 18

Winter tetany: late gestation/early lactation

Grass tetany: lactating cows on lush spring or fall pasture

Question 19

Why does lush spring pasture cause grass tetany?

Answer 19

High concentrations of potassium decrease the absorption of Mg from the rumen

High K in diet, fertilizer used on pasture

Question 20

Clinical signs of hypomagnesemia

Answer 20

• Acute death
• Grass tetany: belligerent, ataxic, muscle tremors, protrusion of nictitans membrane, salivation, bruise, seizures, urination…DDX? Rabies
• Winter tetany: Alert down cow, “can almost get up”

Question 21

How can we diagnose hypomagnesemia?

Answer 21

Normal serum Mg: 1.8-3.0mg/dL

Grass tetany: Mg <1.5mg/dL

Winter tetany: low Mg and low Ca

Can use blood, ocular fluid, CSF, or urine

Question 22

Treatment for hypomagnesemia

Answer 22

IV Ca Mg solutions

Oral or enema

Recommended to follow IV treatment w/ oral supplementation as relapses are common

Question 23

How can we prevent hypomagnesemia?

Answer 23

Supplement gestating and lactating beef cows w/ 10-20g of Mg/day

Question 24

T/F: We can alter acid base status of the animal with the amount of cations and anions in the diet

Answer 24

True

Question 25

Can you give an example of how a mineral salt can influence the pH of an animal?

Answer 25

MgCl - Acidifier
MgSO4 - Cathartic
MgOH - Alkalinizer

Can add Mg to the animal in multiple ways, but the effect on the animal will be different

Question 26

If we feed an excess of cations, we are making the cow more _________

Answer 26

Alkalotic

Question 27

If we feed or treat with an excess of strong anions, we can make a cow ___________

Answer 27

Acidic

Question 28

How does acidifying cows lower the risk of hypocalcemia?

Answer 28

Counteract high K diets
Lower blood pH enhances receptivity of PTH receptor