EFFECT OF CANNULATION AND ENVIRONMENTAL-TEMPERATURE ON THE CONCENTRATION OF SERUM CORTISOL IN PREGNANT SOWS

Serum concentrations of cortisol were monitored in 4 100-day-old pregnant sows during and following cannulation through an ear vein and thereafter for 11.5 consecutive days. During this period, the sows were exposed to the following environmental temperatures: 2 days at 18.degree. C and 3 days at 2.degree., 18.degree. and 32.degree. C, respectively. Serum concentrations of cortisol increased significantly during and after cannulation, but returned to basal levels within 4 h indicating that blood samples can be taken subsequently without stressing the animal. The serum concentration of cortisol followed a circadian rhythm when the sows were kept at 18.degree. C. This daily variation was characterized by maximum and minimum concentrations during the morning and evening, respectively. When the temperature was lowered to 2.degree. C, the circadian rhythm of serum cortisol was maintained, but the daily mean levels were higher. On return to 18.degree. C, the circadian rhythm was temporarily disrupted and the mean daily serum cortisol concentration was lowered. Exposure of sows to 32.degree. C increased the daily mean serum cortisol concentration and restored the circadian rhythm but with an inverted pattern. Exposure to different environmental temperatures affected the daily mean level and circadian pattern of serum cortisol of pregnant sows.