[Proteins specific for pregnancy in ruminants]

The bovine conceptus produces numerous signals during early pregnancy but at the present time only one protein (PSPB; pregnancy specific protein B) is detectable in the peripheral blood during the first 30 days of pregnancy. Validation criteria of the RIA for bovine PSPB have been described by Sasser et al. (1986). This review presents the results obtained in ruminants with this assay. In the bovine PSPB concentrations rise continuously during pregnancy. This protein is found in all pregnant animals at 30 days post Al. Among cows with late embryonic mortality (i.e. with high progesterone concentrations on day 21-24) only 30% present detectable PSPB concentrations between 24 and 30 days post Al. When Al are performed before 70 days post-partum, residual post- partum PSPB concentrations (from the previous pregnancy) the day of Al lowers the accuracy of positive results when PSPB RIA is used as a pregnancy test. In sheep and goat the PSPB profiles throughout pregnancy are very similar to the profile observed in the cattle. In these species the PSPB RIA may be used as a pregnancy test after 26 days post Al. In ruminants, measurement of both progesterone and PSPB in peripheral blood plasma or serum can be very useful to study the way in which various factors may chronologically affect embryonic mortality.