Comparison of four methods of pregnancy diagnosis in seasonal dairy herds in the Manawatu

All cows in 6 spring-calving herds were examined for pregnancy using rectal palpation, real-time ultrasonography or enzyme immunoassay of milk samples for oestrone sulfate content [date not given]. A complete set of results was obtained from 2139 cows, of which 1906 (98.1%) were pregnant and 233 (10.9%) were non-pregnant. The sensitivity and specificity values for all cows were 100 and 93.2%, respectively, for rectal palpation, 99.9 and 96.6% for ultrasonography and 96.8 and 88.1% for oestrone sulfate. In a 2nd group of cattle, a milk sample was taken from all cows in 7 herds between 133 and 181 days after mating, oestrone sulfate content measured, and a list of pregnancy status obtained for each animal based on farmer's observations. Complete results were obtained for 975 animals, of which 877 (89.9%) were pregnant and 98 (10.1%) non-pregnant. Sensitivity and specificity values were 85.2 and 79.6%, respectively, for oestrone sulfate and 95.9 and 54.1%, respectively, for farmer's observation..