The use of progesterone and oestrogen concentrations in the diagnosis of pregnancy, and in the study of seasonal infertility in sows

Plasma concentrations of progesterone and oestrogen in sows 18 days after mating were examined, firstly, as a method of pregnancy diagnosis, and secondly, for indication of any abnormal endocrine patterns that may have been involved in the aetiology of seasonal infertility in sows. Progesterone levels were the most relevant indicator of ovarian function. For the diagnosis of pregnancy, progesterone levels were accurate (97%), but for the diagnosis of non-pregnancy, especially where a high degree of early embryonic death and/or cystic follicles was suspected, as in this trial, progesteronc levels were not as accurate (60%). Oestrogen levels were of use only in confirming the type of infertility suffered by non-pregnant sows. This study shows that seasonal infertility in mated sows is a complex of several forms of infertility, each manifest in a common physical symptom of delayed return to oestrus after a normal mating to a fertile boar. The forms of infertility involved appear to be early embryonic death, luteinized ovarian cysts, small ovarian cysts and silent oestrus