Oestrone sulphate measurement in bovine serum during late pregnancy and its relationship with the number of calves born.

A radioimmunoassay developed for the measurement of oestrone sulphate in bovine serum was used to determine levels of hormone in cows. The cows were sampled as part of an embryo transfer programme designed to investigate the production of twin calves. The concentration of oestrone sulphate in serum was higher in cows carrying twin calves, but the difference did not become significant until around 220 days' gestation. The predictive value of the test could be used as a guide to increase feeding of cows pregnant with more than one calf.