Direct radioimmunoassay of serum progesterone for monitoring the reproductive status of large pig herds

The reproductive status of sows was monitored by serum progesterone radioimmunoassay (RIA) in a closed pig herd of 1100 sows, producing for the market. The method proved suitable for monitoring reproductive events (progesterone production during lactation, effect of weaning on the resumption of cycling, successful and unsuccessful inseminations, abortion, etc.) and for diagnosing ovarian disturbances (acyclia, irregular cycle, etc.). A total of 813 inseminations were followed up to determine the time of return to oestrus. The serum progesterone values of blood samples taken from the v. cava cranialis on day 22 after insemination indicated that pregnancy was diagnosed with a reliability of 75.5%, while non-pregnant sows failing to return to oestrus were identified with a reliability of 96.1%. The economic benefits to be derived from the use of this method in a pig herd are discussed.