Plasma concentrations of
estrone sulfate in different breeds of Japanese beef cattle and the relationship between those concentrations and feto-placental growth were examined in order to assess the possibility of monitoring abnormal growth of the fetus. Blood samples were obtained from cows from day 90 of gestation to parturition. The plasma concentration of
estrone sulfate was measured by direct
enzyme immunoassay. From day 180 of gestation, the mean concentration of
estrone sulfate increased gradually and it was drastically elevated after day 240 of gestation with the maximum at day 285. Plasma concentrations of
estrone sulfate on day 240 of gestation was significantly increased in F(1) cows (Holstein Friesian and Japanese Black) compared with those in other breeds of cow. From day 270 to 278 of gestation,
estrone sulfate concentrations of Holstein Friesian cows inseminated by Holstein Friesian differed from those inseminated by Japanese Black. In the cow with
retained placenta, the plasma concentration of
estrone sulfate reached plateau at day 240 of gestation and did not increase thereafter. There was no significant relationship between
estrone sulfate concentration and duration of gestation, calf
birth weight, weight of placenta or viability of newborn calves. These results indicate that changes of plasma
estrone sulfate concentration in Japanese beef cattle are very similar to those in Holstein dairy cattle. They also suggest that the plasma concentration of
estrone sulfate is associated with the breed of pregnant cow and that its concentration is also affected by calf
birth weight depending on the breed of bull. It seems possible to predict the incidence of
retained placenta but not the calf
birth weight and viability of newborn calves in Japanese beef cattle.