The effect of nose rings on the exploratory behaviour of outdoor gilts exposed to different tests

Rooting behaviour appears to be an important part of the behavioural repertoire in pigs. It is suggested that it is in fact a behavioural need. The present study investigated whether nose-ringed gilts, which are unable to root, can satisfactorily substitute rooting with other exploratory activities. The behaviour of 24 gilts in groups of three, half of them nose-ringed, was studied on undisturbed days as well as on days of exposure to four different tests: (1) delayed feeding; (2) double feeding; (3) removal to an unknown area; (4) removal to an unknown area supplied with a trough with stones. The gilts’ posture and their behaviour were recorded by 1-min scan samplings, whereas pawing, aggression, and comfort behaviour were recorded by all occurrence sampling. Observations took place for 2.5 h in the morning and 2.5 h in the afternoon. On undisturbed days no significant differences were found between ringed and unringed gilts as regards the percentage of scans in which the gilts were active and foraging or exploring. However, the unringed gilts rooted significantly more than the ringed gilts <F>(P<0.01)</F>. The kind of foraging and exploratory behaviours that the ringed gilts chose as substitutes for rooting depended on the replicate in question, maybe due to more or less nutrition in the grass. On an undisturbed day, there was no significant difference as regards the number of times ringed and unringed gilts were observed performing any behaviour that could be considered a sign of frustration. During delayed and double feeding, ringed and unringed gilts reacted similarly. When exposed to an unknown area, ringed gilts increased the levels of alertness and comfort behaviour, which might indicate frustration. We conclude that in a stable environment ringed gilts were able to substitute other exploratory behaviours for rooting in a satisfactory way. However, it was clear that the gilts that were able to root did so for a large part of their active time, indicating that the experience obtained by rooting was rewarding. [Copyright &y& Elsevier]