Endocrine Physiology of the Puerperal Sow2

Measurement of plasma content of corticoids, progesterone, estrone (E1), estradiol (E2) and the Effective Thyroxine Ratio (ETR) was done on samples collected from day 7 prepartum to day 7 postpartum in 23 sows. Competitive protein-binding methods were used for the steroids and the ETR was determined using the Res-O-Mat ETR test (Mallinckrodt, St. Louis). Corticoids reached a peak mean level of 101.8 ng/ml at day 0. There was a significant elevation of corticoids on days −1,0 and +1 when compared to all other days. Progesterone levels began to decline on day −5, reached 0.5 ng/ml by day +1 and remained quite constant thereafter. Estrone increased from 1,139 pg/ml at day 6 prepartum to 2,368 pg/ml at day 2 prepartum. The level of E1 declined to 6 pg/ml by day 6 postpartum. During this same period E2 levels were 46 pg/ml at day 6 prepartum, 75 pg/ml at day 2 prepartum and 5.5 pg/ml at day 6 postpartum.