Abstract
The purpose of this study was to measure the serum content of progesterone, estradiol 17${\beta}$ and cortisol. Blood samples collected from day 20 prepartum to day 20 postpartum in 8 sows. Progesterone and estradiol-17${\beta}$ were assayed by radioimmunoassay methods and cortisol was determined by competitive protein-binding methods. Progesterone levels began to decline on day -4, reached 1.9ng/ml by day +2 and remained quite constant thereafter. Progesterone levels remained fairly constant(18.4 to 20.0 ng/ml) from 20 to 6 days before parturition. Estrdiol-17${\beta}$ increased from 205 pg/ml at day 6 prepartum to 425 pg/ml at the time of parturition. Cortisol reached a peak level of 86.5 ng/ml at day 0.
