Plasma cortisol response in dairy cows to vaginoscopy, genital palpation per rectum and artificial insemination

Response of plasma cortisol concentrations after vaginoscopic examination, palpation of the genital organs per rectum and artificial insemination were investigated in six Holstein-Friesian cows weighing between 510 to 620 kg. Blood samples were collected by indwelling jugular catheter. The experiment was begun at 09:00 hours on the day when cows came into estrus. Blood samples were collected from 30 minutes before to 60 minutes after each treatment at intervals of 5 to 10 minutes. Cows were initially blood-sampled for 90 minutes at the same intervals without giving any treatment and then were subjected to vaginoscopy for 1.5 minutes, palpation of the uterus and ovaries per rectum for 4 minutes and artificial insemination by the recto-vaginal method for 5 minutes. No significant increase in plasma cortisol was shown in cows in estrus following vaginoscopy. Palpation per rectum as well as artificial insemination caused a significant increase in plasma cortisol (P < 0.01) 5 to 10 minutes after the initiation of treatments in cows in estrus. There was a tendency for cows in the luteal phase to show higher plasma cortisol levels after the vaginoscopy than cows in estrus. Adrenal response to palpation per rectum in cows in the luteal phase was similar to that in cows in estrus. Thus, in cows in estrus, palpation per rectum as well as artificial insemination may be potential stressors for cows, causing an increase in plasma cortisol levels. However, the pathophysiological importance of the rise in plasma cortisol levels is not known.