Herd health investigation 3

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Herd health investigation 3

• Mark Stevenson
• EpiCentre, IVABS, Massey University, Palmerston
  North
• M.Stevenson_at_massey.ac.nz

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Herd health

• What this series of lectures will cover
• Lecture 1
• multifactorial nature of disease
• investigating problems and implementing
  interventions
• Lectures 2 and 3
• causation
• measures of health
• Lecure 4
• case studies
• tools for herd health investigations

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Roadmap

• Case study 1

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Case study 1

• Background
• October 2003
• 580 cow spring-calving Jersey herd in the
  Wairarapa
• too many cows went down after calving
• most respond to intravenous calcium the others
  refuse to get up and have to be euthanased
• seems to have been a problem over the last couple
  of years

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Case study 1

• Do we have a problem?
• When did the problem start?
• Define the problem more specifically

MAYBE
ONGOING
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Case study 1
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Case study 1

• What is the problem?
• recumbency in freshly calved cows
• Is there a true excess of disease?
• 60 cases of recumbency August October 2003
• incidence risk 60 580 10 cases per 100
  calvings
• target less than 5 cases per 100 calvings
• yes, there is an excess of disease

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Case study 1

• Establish a case definition
• need to differentiate hypocalcaemia from
  undifferentiated recumbency
• hypocalcaemia classic signs, response to
  intravenous calcium if treated within 6 hours
  of recumbency
• undifferentiated recumbency ?
• Enhance surveillance
• probably not of immediate importance at this
  time, since all cows have calved

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Case study 1

• Describe problem in terms of animal, place and
  time
• who is at risk of disease?
• do we have sufficient records to identify certain
  age groups, those with history of disease, or
  high or low producers as risky
• Generate and test hypotheses
• faulty transition cow ration (? hypocalcaemia)
• inappropriate delivery of concentrates fed on
  rotary (? subclinical and clinical acidosis)

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Case study 1

• What to do next?
• attend to ration delivery issues
• evaluation of the ration indicates (on paper at
  least) that not feeding concentrates while cows
  are on rotary would
• have little effect on daily nutrient intake
• ? feed costs
• because Im cautious I advise to decrease the
  amount of concentrates fed over a period of 10
  14 days and monitor bulk milk tank yields

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Ration evaluation tools
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Ration evaluation tools
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What will we do to daily nutrient intake if we
remove the concentrates fed on the rotary?
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What will we do to daily nutrient intake if we
remove the concentrates fed on the rotary?
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Case study 1

• Comments
• thorough history farm walk required to
  understand this farms system
• assessment of ration feed delivery an important
  part of workup
• case definition essential so situation could be
  monitored more objectively
• next step get things set up to ensure that dry
  cow and transition cow diets are appropriate in
  the coming season

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What was the effect of removing the concentrates
on avarage daily milksolids yield?
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What was the effect of removing the concentrates
on avarage daily milksolids yield?
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Case study 1

• Comments
• concentrate feeds are a good thing, but they must
  be delivered to the cows properly!
• we needed to get the herd manager used to the
  idea that his cows would be OK if they didnt
  receive concentrates now (October 2003) was a
  good time to do this, rather than waiting until
  next calving season
• 12 cases of recumbency July August 2004 ( 200
  calvings)
• incidence risk 12 200 6 cases per 100
  calvings
• have we made a difference?

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