The effect of nose ringing on exploratory behaviour in gilts
Outdoor sows with nose rings can perform most of their natural behavioural activities except rooting. The prevention of rooting through surgical intervention (nose ringing) may be detrimental to welfare, although the behavioural and welfare consequences of rooting deprivation are not well documented. The present experiment examines exploratory behaviour in unringed, ringed and deringed gilts by repeatedly exposing the gilts to a sandbox supplied with bark chips. Four months prior to the experiment, 16 gilts, eight with nose rings and eight without, were housed in four fields. Over a period of 12 days, the 16 gilts, in pairs from the same field, were walked to the sandbox; each gilt visited the sandbox six times in total. After deringing of the ringed gilts (and a control procedure for the unringed gilts), all of the gilts were exposed to the sandbox twice. During each visit, the exploratory behavioural patterns of rooting, sniffing, manipulating, and chewing were observed using 30 s scan sampling. The ringed gilts showed no rooting behaviour in the sandbox; on the other hand, their mean frequency of chewing behaviour was significantly higher than that of the unringed gilts (19.89 versus 13.54; P < 0.05). When all of the exploratory behavioural patterns were summed, no significant differences were found between ringed and unringed gilts. On the second day after deringing, the previously ringed gilts started to root, and no significant difference in the incidence of rooting behaviour between unringed gilts and newly deringed gilts was found. We discuss whether rooting behaviour can be substituted by chewing in order to explore an environment. Gilts that are prevented from rooting are found to explore as much as rooting gilts, and they achieved an adequate knowledge of the sandbox (as demonstrated by the fact that they did not show increased exploration after deringing), although rooting was the preferred exploratory behaviour. In this study, we did not find serious symptoms of chronically reduced welfare as a result of nose ringing.
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