THE ADAPTATION OF HILL LAMBS TO HOUSING CONDITIONS

Sixty Scottish Blackface weaned castrated male lambs, reared under ext ensive management conditions with minimal human contact, were used to study behavioural and physiological responses to housing and increased contact with humans. At the start of the study, the mean age of the l ambs was 20 weeks. One group of 12 lambs was tested immediately at the commencement of the study, one group remained in an extensive environ ment for 12 weeks while the other three were housed for 1, 4 or 12 wee ks after which behavioural and physiological tests were conducted. Dur ing testing, lambs were subdivided into three groups. We recorded the responses of lambs in a 3 m x 3 m open-field arena (divided into nine 1 m squares) and recorded the number of squares entered over standard recording periods and the latency to move both in the absence and the presence of a human. The willingness of lambs to become isolated from their subgroup and the length of time spent facing the human were also recorded. Compared to lambs tested at the start of the study, lambs t ested at the end of the 12-week study entered more new squares when a human was absent (P < 0.05) and subsequently tended to spend more time facing a human when he entered the test pen. There was also some evid ence that, apart from age effects, post-weaning housing resulted in an initial decrease in the latency of the lambs to move and an increase in the number of new squares entered when a human was present, althoug h these differences became less marked as the length of housing increa sed. Overall, lambs entered more new squares during the first 2-min pe riod in the open-field arena (P < 0.001), compared to the following fo ur 2-min periods, but remained tightly bunched over the 10-min observa tion. Once a human entered the test pen, lambs from all groups were re luctant to move from locations furthest from the human, but of the hou sed groups, those housed for only 1 week were quickest to move. Lambs that had not been housed entered fewer new squares. There was no signi ficant difference between the treatment groups in adrenal responsivene ss las assessed using an ACTH stimulation test). It is concluded that both increasing age and post-weaning housing produced some differences in the behavioural responses of the lambs in an open-field arena, but there were no accompanying differences in adrenal responsiveness. (C) 1998 Elsevier Science B.V. All rights reserved.