Two groups of five sheep (7 months of age) were moved and isolated in
pens which did not allow visual and tactile contact with other sheep f
or 24 h. They were then moved back to their original pens where visual
and tactile contact was possible. After 24 h the procedure was repeat
ed seven times for one group (group 8-I) and thirteen times for the ot
her group (group 14-I). One group (control) of five sheep remained in
pens where visual and tactile contact was possible. When isolated the
lambs spent more time standing still in an alert posture, less time ea
ting and resting, and vocalized more than control lambs. The heart rat
e of the lambs increased when they were moved between pens and during
isolation. The plasma concentration of cortisol was significantly incr
eased after 1.5 h and 3 h of isolation. The plasma concentration of pr
olactin was increased after 1-5 h of isolation. After 3 h of isolation
the number of neutrophils in the blood was increased and the numbers
of T-lymphocytes (CD2), T-helper-lymphocytes (CD4) and gammadelta-lymp
hocytes (T19) were decreased. After 24 h of isolation the lymphocyte b
lastogenic response to Con A was lower and the numbers of T-lymphocyte
s and T-helper-lymphocytes were still less than those in control lambs
. Although there were still behavioural changes when the lambs were is
olated for the seventh time, no cortisol, prolactin and leucocyte chan
ges were found. These results suggest that stressors similar to isolat
ion, which can occur during normal management practice, may elicit sho
rt-term leucocyte changes in lambs.