Pathophysiology and treatment of calf diarrhoea

Question 1

Diarrhoea is the failure of?

Answer 1

Net intestinal uptake of water and sodium such that the colon is overwhelmed

Question 2

What are the 4 pathophysiological consequences of diarrhoea?

Answer 2

Dehydration/hypovolaemia
Metabolic acidosis
Hyperkalaemia
Hypoglycaemia

Question 3

Dehydration/hypovolaemia leads to?

Answer 3

Pre-renal failure and shock

Question 4

How does metabolic acidosis occur in diarrhoea?

Answer 4

• Loss of HCO3 (bicarbonate) into gut
• L-lactic acid from tissues
• D-lactic acid from colonic fermentation

Question 5

Hyperkalaemia occurs secondary to?

Answer 5

Acidosis

• Intracellular uptake of H+ (exchange for K+)
• Inhibition of Na+-K+ pumps
• Fatal

Question 6

Describe the features of less than 5% dehydration

Answer 6

• Normal demeanour
• No eyeball recession
• Less than 1 skin tent duration
• very slight increase in total protein

Question 7

Describe the features of an 8-10% dehydration

Answer 7

• Depressed
• 4-6mm eyeball recession
• 2-5s skin tent
• 1.2g/dL increase in TP

Question 8

Describe the features of a more than 12% dehydration?

Answer 8

• Comatose/dead
• 8-12mm eyeball recession
• > 10 second skin tent
• 1.5+ increase in TP

Question 9

What % of dehydration has a skin tent of 5-10 seconds?

Answer 9

10-12%

Question 10

How can acid/base disturbances be diagnosed in a lab?

Answer 10

1. Blood gas machine - pH, pCO2, BIC, TCO2
2. Harleco apparatus measures TCO2 (= BIC).
3. pH meter - gives no indication as to type of disturbance - metabolic and / or respiratory.

Question 11

How can you tell if an acidosis is metabolic or respiratory?

Answer 11

If it was respiratory then pCO2 would be greater than 40 (normal)

Question 12

PCV is elevated in diarrhoea due to?

Answer 12

Dehydration

Question 13

Why is HR increased in diarrhoea?

Answer 13

Increased potassium due to pre-renal failure

Question 14

Are older or younger calves more commonly acidotic?

Answer 14

Older more than 6 days old

Question 15

What are the targets that need to be corrected by fluid therapy in a diarrhoeic calf?

Answer 15

• Hypovolaemia
• Metabolic acidosis: hyperkalaemia
• Hypoglycaemia
• Pre-renal failure

Question 16

What are some key principles/features of fluid therapy in diarrhoea therapy

Answer 16

• Start early, as soon as signs show
• Follow the directions for commercial products
• Typically feed 5% BW per dose, which is around 2L
• Only use an oesophageal feeder if necessary and do not repeatedly use
• Do not withhold milk replacer – not enough energy in fluid therapy alone

Question 17

Oral electrolyte solutions must fulfil which four major requirements?

Answer 17

1. Supply sufficient sodium to normalize the ECF volume (should contain Na+ between 90 and 130 mmol/L)
2. Provide substances (glucose, citrate, acetate, propionate, or glycine) that facilitate absorption of sodium and water from the intestine
3. Provide an alkalinizing agent (acetate, propionate, or bicarbonate) to correct the metabolic acidosis usually present in calves that have diarrhoea
4. Provide energy, because most calves that have diarrhoea are in negative energy balance

Question 18

Name two alkalising agents in fluid therapy

Answer 18

Acetate

Propionate

Question 19

Compare the advantages of acetate and propionate as alkalising agents over bicarbinate

Answer 19

• Acetate and propionate facilitate sodium and water absorption in the calf small intestine, whereas bicarbonate does not.
• Acetate and propionate produce energy when metabolized, whereas bicarbonate does not.
• Acetate and propionate do not alkalinize the abomasum, whereas bicarbonate does; low abomasal pH is a natural defence mechanism against bacterial proliferation.
• Acetate and propionate do not interfere with milk clotting in calves, whereas bicarbonate may potentially cause some disturbance of the normal digestive process

Question 20

When should oral fluids be given?

Answer 20

As soon as scour starts

Question 21

How should oral fluids be administered?

Answer 21

Teat and bucket

Question 22

How often should oral fluids be administered?

Answer 22

Little and often

WITH milk feeding

Question 23

What are the advantages of oral fluid therapy in calves?

Answer 23

Feed the calf - Maintains body condition, Energy for immune response

• Feeds the gut mucosa: assists in repair (glutamine etc)
• Ensures intake of Ca, Mg, vitamins etc.

Question 24

What are the disadvantages of oral fluid therapy in calves?

Answer 24

• May worsen diarrhoea via colonic overload with partially digested foodstuffs.
• May worsen acidosis via colonic fermentation.
• May discourage farmer compliance since treatment appears not to work (volume in = volume out)

Question 25

Name some oral rehydration products

Answer 25

Liquid Life-Aid
Scour Formula Extra
Lectade

Question 26

Which calves may need IV fluid therapy?

Answer 26

• Calves unable to stand.
• Severely acidotic but minimally dehydrated calves
• Calves failing to improve despite oral fluids.
• Very severely dehydrated calves even if standing.

Question 27

Describe volume expanding fluids

Answer 27

‘Balanced fluids’ or isotonic

• Plasma like
• NaCl
• NaHCO3

Question 28

Describe hypertonic solutions

Answer 28

Sodium bicarbonate (5%)
Sodium bicarbonate (8.4%)
Saline (7%)

Question 29

Which solution is most appropriate for initial correction of hypotonic dehydration (electrolytes, predominantly Na+ and K+, lost in scours).

Answer 29

Hypertonic solutions

Question 30

What is the best alkalinizing agent in iv fluids because metabolism of organic base (lactate, acetate etc.) compromised in dehydrated animal.

Answer 30

Bicarbonate

Question 31

If you have a calf less than one week old that is more than 8% dehydrated what do you do?

Answer 31

Give 5L of saline with 250mEq of bicarbonate added

Question 32

If you have a calf more than one week old that is more than 8% dehydrated what do you do?

Answer 32

Give 5L of saline with 500mEq of bicarbonate added