ARS | Publication request: Functional test of the hypothalamic-pituitary-adrenal axis of sows housed in various environments

Submitted to: International Society of Applied Ethology
Publication Type: Abstract Only
Publication Acceptance Date: April 25, 2007
Publication Date: N/A

Technical Abstract: The objective of this study was to assess the behavioral state of sows housed in various housing systems, and determine if the regulation of their hypothalamic-pituitary-adrenal axis had been altered. In Experiment 1, 33 sows were housed in either gestation stalls, group housed with no bedding, or group housed with bedding. A 10 mL blood sample was collected at 1800 h. Immediately following blood collection, 2 mg of dexamethasone was administered i.v. Twelve hours later, a second blood sample was collected. In Experiment 2, all 14 sows were stall housed. Behavioral data was collected weekly on 3 separate days. At 0830, 1 h after sows were fed. Behavioral assessments were conducted to determine the incidence and type of stereotypic behavior that each sow performed. Dexamathasone was administered as in Experiment 1 with blood collection at 2000 h and 0800 h the following morning. Baseline concentrations of plasma cortisol varied among treatments in Experement 1, with stall housed sows having a greater baseline (P < .05) than grouped sows without bedding. Sows in all three treatments showed a similar decrease in plasma cortisol. Ten sows from Experiment 2 performed stereotypic behaviors during 50 % or more of the observations. Dexamethasone suppressed plasma cortisol in 11 sows who exhibited base concentrations of 37.4 ± 4.9 ng/mL which were decreased to 9.9 ± 1.2 ng/mL by 12 h later. Three sows proved to be resistant to the dexamethasone. These sows exhibited base concentrations of 44.6 ± 14.7 ng/mL, which increased to 57.8 ± 13.4 ng/mL by 12 h later. The incidence of oral stereotypic behaviors were not associated with suppression of cortisol (P > .10). Sows were responsive to the suppression of cortisol by dexamethasone. Some sows were not responsive, but this characteristic does not appear to be related to the performance of stereotypic behavior.