EFFECT OF FETAL MASS, NUMBER AND STAGE OF GESTATION ON PREGNANCY-SPECIFIC PROTEIN-B CONCENTRATIONS IN THE BOVINE

In this study we characterized the peripheral plasma pregnancy-specifi c protein-B (PSPB) profile throughout gestation and examined the effec t of stage of gestation, fetal mass and number on this profile in Hols tein cows after non surgical embryo transfer. Cows (n=12) were divided into 2 groups: Group 1=single embryo recipient cows (n=5), Group 2=tw in-embryo recipient cows (n=7). Blood was collected approximately ever y third day from Day 0 (Day 0=first day of standing estrus), then dail y for the last 10 d of gestation, and sampling was stopped 1 d post pa rtum. Two twin-embryo recipient cows had abnormal pregnancies; therefo re, their data were excluded from the group. The time trend concentrat ions of plasma PSPB were significantly affected by the stage of gestat ion (P<0.001) and fetal number (P<0.001). In both groups PSPB increase d gradually, with the mean levels being significantly higher (P<0.01) in the twin-bearing group from Day 50 onwards (0.7+/-0.2 vs 9.2+/-4.5 ng/ml, singleton and twin-bearing cows, respectively) except for Day 1 0 pre-partum. By mid-gestation (Day 140), mean PSPB levels increased i n the singleton (P<0.001) cows by thirty-fold (21.2+/-3.2 ng/ml) as op posed to a ten-fold (98.4+/-13.2 ng/ml) increase in the twin-bearing ( P<0.001) group. The mean PSPB concentrations between Days 30 to 20 pre partum dramatically increased by about 700 to 200% in singleton (128.8 +/-46.3 to 745.6+/-66.7 ng/ml) and twin-bearing cows (375.6+/-130.4 to 861.5+/-127.9 ng/ml), respectively. The PSPB levels between Day 10 pr epartum to parturition were significantly higher (P<0.001) in the twin -bearing group than in the singleton group (745.6+/-66.7 to 1627.4+/-2 38.9 ng/ml vs 861.5+/-127.9 to 3103.0+/-643.0 ng/ml in singleton and t win-bearing groups, respectively). Calf birthweight was correlated (P< 0.01) to peripheral PSPB concentration in singleton cows; however, thi s relationship decreased with the subsequent increase in fetal number. Cows giving birth prematurely to stillborn calves or to a schistosomu s reflexus calf exhibited abnormal PSPB profiles. These results indica te that peripheral PSPB levels are correlated to the stage of gestatio n and fetal number. In addition, the peripheral pattern of PSPB is a v aluable guage for predicting fetoplacental viability.