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A note on simulating the 'observer effect' using constant photoperiod on nursery pigs

By D. C. Lay, H. S. Buchanan, M. F. Haussmann

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Often, researchers using video cameras to record animal behaviour must resort to illuminating the environment to obtain data during the night hours. This study was designed to determine if the behaviour of pigs is altered by constant illumination. Pigs (24+or-0.95 days of age, 5.58+or-0.18 kg) were randomly assigned to 1 of 2 groups. Treatment pigs were exposed to a constant photoperiod (24:0, light:dark cycle) while control pigs were exposed to a 12:12 light:dark cycle (lights on at 06.00 h and off at 18.30 h). 30 pigs for each treatment were randomly assigned to 1 of 6 pens, blocked by sex, so that each pen contained 5 pigs (2 females and 3 males). Pigs were acclimated to the photoperiods for 1 week, and during this time, no observations were made. After this period, the activity of both treatments was recorded by video cameras for 6 days. Upon completion of this week of observation, the photoperiod for all pigs were reverted to the 12:12 light:dark illumination schedule for 1 week, after which observations resumed for an additional 6 days (days 14 to 19). The 24:0 pigs were more active than the 12:12 pigs between 18.30 h and 06.30 h. This increase in night time activity resulted in a trend for 24:0 pigs to be more active during the entire day. The 24:0 pigs were most active during the first 3 h and last 3 h of observation from 18.30 h to 06.30 h. It is concluded that constant illumination caused an alteration in the behaviour of pigs during video recording effectively simulating the 'observer effect'. Altering the activity budgets of experimental animals could have profound effects on experimental results as alterations in activity may lead to alterations in eating behaviour, agonistic encounters and levels of social stress.

Date 1999
Publication Title Applied Animal Behaviour Science
Volume 63
Issue 4
Pages 301-309
ISBN/ISSN 0168-1591
DOI 10.1016/S0168-1591(99)00018-0
Language English
Author Address Iowa State University, Department of Animal Science, 2356 Kildee Hall, Ames, IA 50010, USA.
Cite this work

Researchers should cite this work as follows:

  1. Activity
  2. Animal behavior
  3. Behavior and behavior mechanisms
  4. Illumination
  5. Light
  6. Lighting
  7. Mammals
  8. peer-reviewed
  9. photoperiodism
  10. Pigs
  11. recording
  12. Swine
  13. video recordings
  1. peer-reviewed