Comparison of serum cortisol and prolactin in sheep blood sampled by two methods

Abstract

The objective was to compare serum cortisol and prolactin levels in sheep following remote blood sampling with levels after the animals were handled. Twelve ovariectomized ewes were studied during two consecutive years. Each year, six ewes were kept in metabolism crates inside a building for 1 month. During this period they were accustomed to being handled. Prior to sampling, sheep were assigned to two groups (A and B) of three. Group A animals were fitted with an iv-catheter in one jugular vein (conventional sampling) and a 4 m long polyvinyl cannula in the other jugular vein (remote sampling). Group B animals were fitted only with the iv-catheter. In the first part of the study, group A sheep were sampled remotely and undisturbed for 3 hr at 10-min intervals and immediately afterwards were sampled conventionally for an additional 3 hr at 10-min intervals. In the second part of the study, group A animals were sampled remotely while group B animals were sampled conventionally for 3 hr at 10-min intervals. During this sampling period, group A animals, although not handled, were aware of disturbances in the sampling room. Serum cortisol (28.6 ± 0.9 vs. 11.8 ± 0.7; x ± SEM ; ng/ml) and prolactin (58.1 ± 3.6 vs. 32.7 ± 2.9; x ± SEM ; ng/ml) levels were higher (P<.05) when samples were obtained conventionally than when samples were obtained remotely and undisturbed. In spite of disturbances during sampling, cortisol (9.1 ± 0.6 vs. 18.9 ± 0.8; x ± SEM ; ng/ml) and prolactin (38.3 ± 2.9 vs 59.6 ± 5.6; x ± SEM ; ng/ml) levels in samples obtained remotely (group A) were lower (P<.05) than in samples obtained conventionally (group B). Even after previous adaptation, handling sheep during blood sampling caused a significant elevation in serum cortisol and prolactin levels.