Controlling Hypocalcaemia

Question 1

What hormones act to increase blood calcium?

Answer 1

PTH and calcitriol

Question 2

When are cows most at risk for milk fever?

Answer 2

On day of calving, especially heifers

Question 3

What are risk factors for hypocalcaemia?

Answer 3

• Around calving; Ca demand increases rapidly, endocrine control takes a few days to adjust.
  
  • Resorption from the kidneys is the fastest repletion followed by increased intestinal absorption.
  • Release of Ca from bone is the slowest.
• Age of cow; Older cows have reduced calcium reserves and mechanisms respond slower.
• Milk fever risk increases with parity as milk yield increases
  
  • Peaking around 3-4
• Other increased risk factors include;
  
  • C-section, dystocia, BCS ≥4, hereditary.
• Herd risk factors important too
  
  • Eg, dairy crosses (Limousin x Holstein), channel island breeds, autumn calving cows.

Question 4

What clinical signs are typical of hypocalcaemia?

Answer 4

• Skeletal muscle
• Weakness
• S-bend neck
• Smooth muscle
• Rumen atony
• GI stasis
• Poor uterine involution
• Cardiac muscle
• Poor contractility
• Slightly increased HR (c.f. “toxic” cow)

Question 5

What treatment protocol is used for hypocalcaemia?

Answer 5

• 400ml 40% calcium borogluconate slowly IV
  
  • If given too fast inc. risk of hypercalcaemic relapse.
  • Reverses physiological mechanisms.
  • Halts PTH release and triggers calcitonin secretion due to surplus in blood.
  • ~25%-40% relapse within 12 to 24 hours unless dose is managed.
• Monitor heart rate and rhythm.
• Consider blood sample in case no response.
• Outcome of treatment:
  
  • Eructation, defecation, urination & standing within ~20-30 mins
  • If no response, consider alternatives and complications (e.g. “downer cow”)

Question 6

What additional treatments would you administer in a hypocalcaemic cow?

Answer 6

• oral Ca
• NSAIDs
• phosphorus

Question 7

How should you manage mineral intake to reduce the incidence of milk fever on a herd level?

Answer 7

• Decrease Ca in dry period - Limiting Ca prior to calving, up-regulates PTH mechanisms which starts resorption from bone, increases dietary absorption etc. Over 2-3 weeks cow is better prepared for increased demand. Must increase dietary Ca at calving.
• Decrease K in dry period

Question 8

How can we lower blood pH? Why is this important?

Answer 8

• Lowering blood pH can prevent hypocalcaemia.
• This is achieved through reducing DCAB in the dry period.
  
  • Decrease Na+ and K+ (cations), increase Cl- and S- (anions).
• Resulting slight acidosis increases binding of PTH and other effects.
• Improves the cow’s ability to mobilize calcium from the bones and to absorb dietary calcium from the small intestines.