Herd level metabolic disease

Question 1

Which diseases are important at a herd level?

Answer 1

Ketosis and negative energy balance (NEB)

Hypocalcaemia (milk fever)

Question 2

Why does ketosis matter?

Answer 2

Question 3

How can negative energy balance be monitored?

Answer 3

Question 4

What BCS should be aimed for at different periods to reduce the likelihood of ketosis?

Answer 4

Key targets…

• 2.5-3 at calving
• no change during dry period (maintain BC)
• maximum 0.5 drop calving –> peak lactation
• avoid cows >3 at calving

Each cow should get a BCS calving and at peak lactation.

Question 5

How can metabolic profiles be used to monitor ketosis?

Answer 5

• Blood sampling a random group of cows
  
  • At specific stages
    
    • Usually transition cows and fresh calvers
    • (21-7 days pre-calving) (10-25 DIM)
  • Indicators of negative energy balance…
• BHB
  
  • Ketone body
  • Indicates current energy supply/demand
  • Esp. important in fresh calvers
• NEFA
  
  • Transport form of fat
  • Indicates mobilisation of body fat
  • Esp. important in transition cows
• Metabolic profiling:
• How many samples?
  
  • Varies with size of group (e.g. dry cows)
  • BUT not that much!
  • Typically 8-12 samples/group required
• Interpreting results
  
  • Target prevalence of high BHB/NEFA generally <10-20%
  • Usually this means any abnormal results are potentially suggestive of a problem
  • Typically >=3/12 high considered “positive”

Question 6

How can milk parameters be used to measure ketosis?

Answer 6

In neg energy balance the milk protein content tends to go down

Butterfat concentration tends to go up

Question 7

How can ration analysis be used to monitor ketosis?

Answer 7

• Ration analysis
  
  • Estimate feed intake and ration energy density
  • Compare to cow energy requirements
  • Specialist software available

Question 8

How is negative energy balance caused with regards ration at early/peak lactation (type 1) compared to transition/calving (type 2)?

Answer 8

Question 9

How much DMI should 700kg holstein cow get?

Answer 9

• Aiming for… (700kg Holstein cow)
• >23kg DM/day at peak lactation
• >12kg DM/day in transition (late dry) period as approaches calving intake drops off
• 23kg is DRY MATTER intake for the day (could easily be 60kg fresh weight!)

Question 10

What are the ‘sticking plaster’ solutions to ketosis?

Answer 10

Dietary additives that may improve the situation…

• Propylene glycol (alternative glucose source)
• Protected methionine (improves export of fat from liver)
• Linoleic acid (fatty acid with less tendency to accumulate in liver)
• Monensin (antibiotic, changes balance of rumen microflora increases propionate:acetate)
  
  • Available as rumen bolus in UK
  • Licensed for use in “cow/heifer which is expected to develop ketosis”

Question 11

What is a word of warning with making a ration more energy dense with concentrate?

Answer 11

One way to make it more energy dense is to replace with concentrate but be careful as it may push rumen into SARA (acidosis)

SARA: subacute ruminal acidosis

Question 12

How does hypocalcaemia occur?

Answer 12

• Sudden increase in demand at calving (lactation)
• If stores (mainly bone) not mobilised quickly enough…
• Circulating [Ca] falls
• Clinical or subclinical “milk fever”

Question 13

Draw a schematic for calcium mobilisation?

Answer 13

Question 14

How does a drop in plasma calcium cause the problems observed with milk fever?

Answer 14

Question 15

How can hypocalcaemia be diagnosed?

Answer 15

• Clinical signs
• Blood sample (¯plasma [Ca])

Question 16

What is key in preventing milk fever?

Answer 16

Feeding in the final 2-3 weeks before calving is key to milk fever prevention

Question 17

What is a DCAB diet and how does it prevent milk fever?

Answer 17

• Dietary cation-anion balance (DCAB)
• Difference between levels of major cations (Na+, K+) and anions (Cl-, S2-) in diet

DCAB = ([Na+] + [K+]) – ([Cl-] + [S2-])

(all in mEq/kg DM)

• Diets with low DCAB (<0mEq/kg DM) induce mild metabolic acidosis…
• Metabolic acidosis means…
  
  • More vitamin D3 is activated per unit PTH
  • Target tissues (esp bone) are more sensitive to PTH and 1,25(OH)2D3
• So the cow is more able to mobilise Ca from body reserves quickly

Question 18

What is a full DCAB and why is it unfeasible?

Answer 18

DCAB is putting the cow into metabolic acidosis meaning they can uptake calcium from gut better and mobilise it from the bone

• “Full” DCAB approach *making it def neg -100 so will need to monitor urine ph as you can make too acidic if you go too far
• Addition of anionic salts e.g. MgCl2, MgSO4
• Decrease diet DCAB to around -100mEq/kg DM
• Monitor urine pH to check acidification
• But…
  
  • Expensive (~£1/cow/day)
  • Salts unpalatable (need good mixing)
  • Very soluble (wash out in rain!)

Question 19

What is a partial DCAB approach and how is it achieved?

Answer 19

• “Partial” DCAB approach
• Manipulate available feeds to decrease ration DCAB to around 0 to +100 mEq/kgDM
• +/- small amount anionic salt

Question 20

How is calcium restriction used to prevent hypocalcaemia?

Answer 20

Calcium restriction

• Traditional method
• “Conditions” homeostatic mechanisms

so that they are very efficient at mobilisation

i.e. lots of PTH

• Works well if can get Ca intake low enough
  
  • <20g/day ideal (lactating cow needs >100g/day)
  • Some effect at 40-50g/day
• Very difficult to achieve with normal transition diets
  
  • Mainly due to grass/ grass silage (rel. high [Ca])
  • Especially hard to achieve if grazing!
  • Ca binding feedstuffs available