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

2. 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

3. 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;

4. 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.

5. Study Design • Piglets from 4 litters divided into 3 treatment groups: • Hippocampal enhancement (HE, n=9) • Isolation control (IC, n=9) • Sow control (SC, n=9) • 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

6. 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

7. 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

8. 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

9. Study Design: Open Field chair • 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 ball Gate

10. 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

11. 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 < 0.001

13. ‡ 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 < 0.001

15. a b b 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 > 0.05 in all cases)

18. 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.

19. 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