Effect of a Maze Task on Salivary Cortisol of Pigs at Weaning and on Subsequent Fear Response

1
Effect of a Maze Task on Salivary Cortisol of
Pigs at Weaning and on Subsequent Fear Response

• J.M. Siegford, G. Rucker, A.J. Zanella
• Animal Behavior and Welfare Group
• Dept. Animal Science, Michigan State University
• East Lansing, MI 48824

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Introduction

• Learning, memory and regulation of the stress
  response are mediated by the brain region known
  as the hippocampus.
• Learning memory
• e.g., Bannerman et al., 2002 Castro et al.,
  1989 Maaswinkel et al., 1997 Rosenzweig et al.,
  2003
• Stress
• e.g., Blank et al., 2002 Broom Zanella, 2004
  Dachir et al., 1993 Fuchs Flugge, 2003 Kaiser
  et al., 2003 McEwen, 2001

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Enhancing coping responses in pigs

• Biologically relevant hippocampal-dependent tasks
  may help integrate cognitive processes,
  encouraging development of an adaptive stress
  response.
• Cooper Cox, 2001
• Neonatal handling alone does not benefit pigs.
• e.g., Weaver et al., 2000

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Hypothesis

• Performing hippocampal-dependent tasks may reduce
  stress-related physiological and behavioral
  consequences of early-weaning.

Prediction

• Piglets performing a maze task (MT) prior to
  weaning will show less stress at weaning, better
  ability to solve other spatial tasks, and lower
  subsequent fear responses.

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Study Design

• Piglets from 4 litters divided into 3 treatment
  groups
• Hippocampal enhancement (HE, n9)
• Isolation control (IC, n9)
• Sow control (SC, n9)
• Trained and tested in MT from 5-11 days of age
• Number of trials taken to learn maze and time
  taken to solve maze were recorded

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Study Design Maze Task

• 4x/day on days 5-11
• Max of 5 min/exposure and 10 min between exposures

• Piglets trained in
• the maze by
• shaping

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Study Design

• Piglets weaned by litter on day 12
• Piglets tested for spatial memory using a water
  maze task at 14 days of age
• (Laughlin Zanella, 2003)
• Fear response of pigs examined using open field
  tests at 49-51 days of age

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Study Design Water Maze

• Spatial memory task on day 14
• 5 exposures separated by 10 min intervals
• Maximum of 20s to solve the task
• Exposure ends when pig locates and stands on
  platform

• Latency to reach platform is recorded

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Study Design Open Field

• 3 open field (OF) tests over days 49-51
• OF1 alone
• OF2 w/ball
• OF3 w/person
• 5 min total
• 1 min for acclimation
• 4 min of testing

chair
ball
Gate
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Study Design

• Additional measures taken
• Weights taken daily until 21 days of age, then
  weekly until 49 days of age
• Saliva collected before and after the last MT,
  weaning, water maze, and open field tests

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Cortisol Levels at MT

• Saliva was collected immediately before and after
  the MT on day 11 to measure cortisol

P 0.04
12
Cortisol Levels at Weaning
P lt 0.001
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Water Maze

• Male IC pigs were slower to escape the maze than
  pigs of all other groups

P 0.07
14
Fear Response at 50 days

• Pigs spent less time in the center of the open
  field in OF1 compared to OF3

b
a
P lt 0.001
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Fear Response at 50 days

• IC pigs spent more time in the periphery in OF1
  than did IC or HE pigs in OF3

P 0.03
16
Fear Response at 50 days

• In OF3, HE touched the unfamiliar person more
  times than pigs in other groups

P 0.008
17
Body Weights

• No differences were seen in weights of piglets at
  weaning or up to 7 weeks of age (P gt 0.05 in all
  cases)

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Implications

• Handling alone was not responsible for changes
  seen in behavior
• All animals were handled to a similar degree
• MT may result in less fear of novel persons and
  places suggesting benefits of cognitive
  stimulation for young pigs.
• MT did not negatively affect growth of pigs.

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Thank you

• The MSU Swine Teaching and Research Center
• Cheryl Leece
• MSU McNair/SROP Program
• USDA NRI 2001-2440 to A.J. Zanella funded this
  study