The effect of confinement in metabolism stalls on the cortisol, antibody production, and antibody-dependent cell-mediated cytotoxicity of tame lambs

Abstract

Thirty 10-wk-old, Rambouillet wethers were used to evaluate the effect of confinement in metabolism stalls on cortisol and specific and non-specific immune function. All lambs were habituated to human contact and maintained in an outside lot for one month prior to data collection. After taming, the lambs were blocked by temperament score and weight and assigned to either experiment I (EXP I, n = 18) or to experiment II (EXP II,, n = 12). In EXP I, 6 lambs were placed in metabolism stalls on d -7 ("stalled -7"), and 6 lambs were placed in either metabolism stalls ("stalled") or a group pen ("penned") on d 0. All of the lambs were given .5 ml subcutaneous (SC) and .5 ml intramuscular (IM) injections of chicken red blood cells (CRBC) in incomplete adjuvant on d 0. Blood samples were collected via jugular venipuncture at 2 d intervals (d 0 to d 12). Plasma cortisol concentrations and antibody (Ab) production in response to CRBC were determined for all sampling times. There was a significant treatment by day interaction (P < .0001) for plasma cortisol concentrations. Cortisol of "stalled" lambs was significantly higher than "penned" and "stalled -711 lambs on d 0, 6, and 8, but lower than "penned" on d 4. There was no difference between the cortisol of "penned" and "stalled -711 lambs (P > .3) except for "penned" being higher on d 4 (P < .01). The Ab response to CRBC was not influenced by treatments (P > .7). In EXP II, 6 lambs were placed in either metabolism stalls or in a group pen ("stalled" or "penned") on d 0. Plasma cortisol concentrations were determined at 2 d intervals (d 0 to d 12) while mononuclear effector cell activity was determined by antibody-dependent cell-mediated cytotoxicity (ADCC) assays at 0, 4, 8, and 12 d. Cortisol concentrations and mononuclear cell efficiency were influenced by days on treatment (P < .003 and P < .0001, respectively) but not by treatments (P > .4 and P > .8, respectively). The mononuclear effector cell activity of both "penned" and "stalled" animals increased significantly and reached a peak on d 8,, then declined on d 12. Confinement of 10-wk-old lambs in metabolism stalls had a highly variable effect on the pituitary-adrenal and immune system, perhaps reflecting differences in how individual sheep perceived and coped with the treatments.