Evaluation of an ultrasonic amplitude depth analysis technique for pregnancy diagnosis in the cow.

Beef and dairy cows (n = 1,053) were tested for pregnancy on 7 farms by ultrasonic scanning. Accuracy was verified by comparison with rectal palpation. Rectal palpation was done 40 to 75 days after breeding and was considered 100% accurate for comparison purposes. Although diagnostic accuracy of the ultrasonic scanning technique was less than 100%, a confidence interval no larger than 2.3% indicated a high degree of precision for pregnant cows. The confidence interval in the nonpregnant category ranged from 9.2% to 11.8%, which was small in relation to the variation in ultrasonic scanning accuracy. However, considering the large number of cows and the experimental bias that was purposely introduced, the lower accuracy of the ultrasonic method was not unexpected. Cystic ovaries, partially involuted uteri, metritis, and high milk production prevalent at one location accounted for much of the variation observed and lowered the overall accuracy for all cows tested. The ultrasonic analyzer has potential in testing cows for pregnancy; however, technical improvements in machine configuration must be made and additional testing in controlled experiments and field trials must be conducted before an accurate analysis of this method can be made. At the present state of development, ultrasonic amplitude depth analysis cannot replace rectal palpation for diagnosis of pregnancy in cattle.