Pregnancy Specific Protein B as a Predictor of Gestation Length in Angus Cows and Heifers

The objectives of this study were to characterize a relationship between Pregnancy Specific Protein B (PSPB) concentrations and the stage of gestation for cows and heifers and to determine if these concentrations can predict gestation length. Fifty-three multiparous cows and 21 single parity cows were used. The animals were estrus synchronized, bred via artificial insemination, and exposed to a bull to increase conception rates. Blood samples were collected several months throughout gestation and sent to the laboratory to be analyzed through an ELISA. Concentrations of PSPB were recorded for each animal by month and parturition dates. The concentrations measured by optical densities for the month of May had a strong correlation with birth date and birth order (P < 0.001). The strength of the correlation began to decrease with time. Calving probability within the first 31 days of calving season was high for May when optical densities were higher than 0.400. The optical densities of the subsequent months show lower possibilities for predicting calving time.