Changes in peripheral progestagen levels in early pregnant gilts following injection of human chorionic gonadotrophin.

Abstract

The capacity of human chorionic gonadotrophin (hCG) to raise plasma progestagen levels during the first 8 days of gestation in gilts was examined. The effective half-times of hCG in gilts treated with 500 and 5000 i.u. hCG were 29.1 and 26.3 h respectively (P greater than 0.05). Neither 500 nor 5000 i.u. hCG caused rises in peripheral concentrations of progesterone or pregnenolone sulphate, and plasma pregnenolone concentrations declined (P less than 0.05) following hCG treatment. Apart from diminished total corpus luteal weights in gilts treated with 500 i.u. hCG (P less than 0.05) and lower peripheral progesterone levels in gilts treated with 5000 i.u. hCG (P less than 0.05), ovarian and plasma steroid characteristics of hCG-treated animals between 23 and 25 days of gestation were similar to control values. Furthermore, treatment with hCG did not affect embryo survival during the first 4 weeks of pregnancy, and plasma oestrone/oestrone sulphate levels provided no evidence for differences between control and treated animals in trophoblastic outgrowth. These results challenge the rationale for the treatment of early pregnant sows with hCG in order to reduce the levels of embryonic wastage in early pregnancy.