THE RELATIONSHIP BETWEEN HOUSING AND SOCIAL RANK ON CORTISOL, BETA-ENDORPHIN AND DYNORPHIN-(1-13) SECRETION IN SOWS

Endogenous opioids and glucocorticoids may be useful welfare indicator s in pigs, Measures of plasma cortisol were carried out in plasma samp les collected hourly, from 8:00 to 17:00 h from High Ranking (HR) (n = 5) Middle Ranking (MR) (n = 7) and Low Ranking (LR) (n = 4) group hou sed sows and from eight Stall Housed Sows (SHS). Cerebrospinal fluid ( CSF) was collected after pentobarbital injection (n = 17; HR n = 2; MR n = 3; LR n = 4 and SHS n = 8) and the levels of beta-endorphin and d ynorphin monitored. Brains were removed, weighed and frozen. Cortisol, beta-endorphin and dynorphin were measured in extracts of frontal cor tex. LR sows had significantly lighter brains than HR sows (LR = 126.0 5 +/- 2.18 and HR = 144.86 +/- 3.97) and showed no circadian pattern i n cortisol secretion. HR and LR sows had lower cortisol levels than MR sows, There was an indication that HR, MR and stall housed sows tende d to have lower beta-endorphin levels in the CSF than LR sows (0.83 pg /ml +/- 0.39; 1.66 pg/ml +/- 0.472; 1.07 pg/ml +/- 0.267 and 6.81 pg/m l +/- 3.27 respectively). Mean dynorphin (1-13) levels in the CSF were 12.56 pg/ml (+/-5.49). Sows kept in stalls had higher levels of dynor phin in the frontal cortex than group housed sows. (C) 1998 Elsevier S cience B.V. All rights reserved.