The effect of gilts' age on inactivity in a behavioural test

The present study investigated whether gilts' reactivity in an arena test, developed for selecting prepubertal gilts for reproduction, changed with age. One hundred and twenty gilts were used in the study of which 60 were tested at 3 months of age and re-tested at 4.5 months of age and 60 were tested only at 4.5 months of age. During the 3 min arena test the duration of inactivity was recorded by direct observation. The results from the present study showed that gilts were less inactive, when exposed to the arena test at 4.5 months compared to 3 months (57 +/- 9 s versus 92 +/- 10 s; P < 0.05). This change in inactivity was due to an effect of age and not to an adaptation to the test situation since no difference was found between the gilts in the group re-tested at 4.5 months and the gilts in the control group, which had never been exposed to the arena test before (57 +/- 9 s versus 45 +/- 9 s; NS). The measure of inactivity shows some consistency across time (P = 0.052). Thus if a selection of prepubertal gilts is to be made, based on the arena test, the results of the present study show that the selection should be carried out within gilts tested at the same age. (C) 2006 Elsevier B.V. All rights reserved.