Wool-pulling behaviour appears in a production system with grazing restriction and can be assessed through wool inspection

Abstract

Sheep flocks can be reared in different production systems that differ in the duration of indoor housing and grazing restriction. Indoor housing can lead to aggressive interactions, such as blocking, threats and butts, whereas grazing restriction may cause wool-pulling. Wool-pulling is an abnormal behaviour that appears in confined flocks and affects the wool condition of affected animals. Wool condition has been included in some sheep welfare assessment protocols, but in most cases the causes of wool alteration are not addressed. Therefore, it would be useful to establish whether changes in wool condition may be attributable to wool-pulling behaviour. The aim of this study was to find out the effect of grazing restriction on the prevalence of wool-pulling behaviour, assessing wool cover as an indicator of this behaviour, and to analyse the effect of grazing restriction on the prevalence of aggressive behaviours. Two groups of twenty Ripollesa pregnant ewes were used, a temporary grazing group (G) and a permanently housed group (H). Group G had access to pasture daily from 10:00 h to 15:00 h, while Group H remained in the barn throughout the experimental period (10 weeks). The behaviour of all sheep was video-recorded along a ten-week period, two days per week 45 minutes each day, and an ethogram that included wool-pulling, aggressive behaviours, resting and rumination was developed and used. Wool-pulling was observed exclusively in Group H. On the other hand, a four-scale score of wool cover was used to assess wool pulling behaviour, and the score evolved significantly different in both groups. In Group G, no change in wool-cover was observed whereas in Group H, wool-cover change was observed in eleven out of twenty ewes throughout the experimental period. A positive correlation was found (R=0.98, P=0.01) between wool pulling observed by direct observation and wool-cover assessment, and it was concluded that wool cover is a potentially useful indicator of wool-pulling behaviour. The frequency of aggressive behaviours was higher in Group H than in Group G during the entire experimental period (35 ewes vs. 11, P=0.04), which suggests that it was caused by grazing restriction.