Accuracy of laying hens in jumping upwards and downwards between perches in different light environments
Eighty Lohmann Brown layer hens were reared in floor pens fitted with perches from 1 day of age. After the peak of lay (25 weeks of age), their ability to jump to and from perches in different light environments was assessed in two experiments using digital video techniques that allowed detailed measurements of take-off, flight and landing behaviours. In Experiment 1, birds jumped up or down (angles of 10 and 18°) between two horizontal perches that were separated by a gap of 60 cm under different lighting conditions (5, 10 or 20 lux; incandescent or high- or low-frequency fluorescent). In Experiment 2, the horizontal distance was increased to 80 cm and contrast between perch and background was varied. Fifty-two hens (65%)achieved the training criterion for Experiment 1: jumping a 60 cm gap five times of which three in a row. Thirty-two of these hens (62%) subsequently failed to achieve the 80 cm jump criterion for Experiment 2. In Experiment 1, birds took off sooner (P < 0.001), turned their heads further downward relative to the landing perch (P < 0.001), beat their wings more often during flight (P < 0.001), and took longer to achieve balance (P < 0.001) when jumping downward rather than upward. In Experiment 2, refusals to jump, and clumsy or missed landings, occurred more frequently on downward than upward jumps (P < 0.001). These behaviours were unaffected by lighting conditions, or by the amount of contrast between the perch and its background. In conclusion, behaviours indicating inaccurate control of landing were more frequent on downward than on upward jumps (P < 0.001). However, these behaviours were not affected by light intensity, light type or contrast. The results suggest that there is a difference between the two types of jumps in the risk of injury to hens housed in aviaries where perches must be used to gain access to resources.
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23 August 2010
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