EFFECT OF METHOD OF BLOOD-SAMPLE COLLECTION ON ADRENAL ACTIVITY IN FARMED RED DEER AND SHEEP FOLLOWING ADMINISTRATION OF ACTH

The effect of method of blood sample collection (automatic blood sampl ing equipment (ABSE) v. manual) on cortisol and progesterone concentra tions was investigated in 20 farmed red deer hinds and 20 domestic she ep ewes following dexamethasone and exogenous ACTH administration. Ten animals were subjected to either automatic sampling or manual samplin g via jugular venipuncture in I week, with the treatment groups revers ed in the 2nd week. The ABSE was programmed to collect a blood sample, then deliver 2 mg dexamethasone, collect a further blood sample 120 m in later and then inject 100 mu g ACTH. Thereafter, samples were colle cted at 15-min intervals during a 2.5 h period (12 samples in total). In the manual injection and sampling treatment, four samples were coll ected: (1) before dexamethasone administration, (2) before ACTH admini stration, (3) 60 min after ACTH administration, and (4) 150 milt after ACTH administration. The success rate of blood sampling with ABSE was 80%. The overall mean packed cell volume (PCV) from samples collected by ABSE from both hinds and ewes was significantly lower than that fr om samples collected manually (P < 0.01) and PCV declined with time in manually sampled animals (P < 0.01). Plasma cortisol concentrations p eaked at 45 min after ACTH administration in sheep and deer. In sheep, there was a marked fluctuation in the plasma cortisol concentrations with time. Both deer and sheep showed a reduced cortisol response to A CTH during week 2 irrespective of sampling method suggesting down-regu lation of the response to ACTH. Maximum mean plasma progesterone conce ntration was reached at 15 to 30 milt after ACTH administration. No si gnificant differences in cortisol and progesterone responses due to bl ood sampling method were found in animals receiving prior dexamethason e treatment. This demonstrates that the ABSE has the ability to be use d to effectively conduct ACTH stimulation tests without the need to ha ndle the animals during the test.