Confinement of lambs ( Ovis aries) in metabolism stalls increased adrenal function, thyroxine and motivation for movement

Abstract

Eighteen, 8-week-old Rambouillet wether lambs were habituated to human contact for 2 months prior to data collection. The lambs were maintained in a paddock prior to being placed in individual 41 cm × 95 cm metabolism stalls for 9 days. Blood samples were taken via jugular cannulae 7 days prior to, and after 2 and 9 days of confinement. After two basal blood samples were drawn, 1 iu kg −1 adrenocorticotrophic hormone (ACTH) was administered to each lamb via the cannulae and serial blood samples were drawn over the next 3 h. A 5-min open-field test was conducted the day before the lambs were placed in stalls and again after Day 9, following the last blood sampling. Response to ACTH, measured as the integrated cortisol concentrations, was greater when the lambs were housed in stalls than maintained in the paddock ( P < 0.01). Confinement did not affect plasma concentrations of triiodothyronine ( P < 0.37), but lambs in stalls had higher concentrations of thyroxine after 2 and 9 days than when on pasture ( P < 0.001). Lambs traveled further during the open-field tests, after 9 days in the metabolism stalls, than they did before confinement ( P < 0.001). These results indicate that lambs maintained in metabolism stalls can be physiologically and behaviorally altered. Such alterations may affect the applicability of certain types of data derived from these lambs compared with lambs in more extensive housing situations.