Peripheral cortisol levels throughout gestation in the cow: effect of stage of gestation and foetal number.

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