PERIPHERAL CORTISOL-LEVELS THROUGHOUT GESTATION IN THE COW - EFFECT OF STAGE OF GESTATION AND FETAL NUMBER

This study characterized tile peripheral plasma cortisol profile throu ghout gestation and examined the effect of stage of gestation and foet al number in Holstein cows after non-surgical embryo transfer. Cows (n =10) were divided into two groups: Group 1=single embryo recipient cow s (n=5); and group 2=twin-embryo recipient cows (n=5). Mean plasma cor tisol concentrations remained basal (2-4 ng ml(-1)) in both groups up to 2 days prepartum increased significantly (P < 0.05) to peak at part urition day, and then declined rapidly 1 day post-partum. Twin-hearing cows had significantly (P < 0.01) higher mean plasma cortisol concent ration on the day of parturition than in the singleton cows. There was no effect of the stage of gestation on cortisol levels in either grou p (P > 0.1), except in the last 48 h prior to parturition. A single co w giving birth prematurely had 100% higher plasma cortisol levels on t he day of parturition and 1 day post-partum than cows giving birth at term.