FACTORS INFLUENCING THE ACCURACY OF EARLY-PREGNANCY DETECTION IN CATTLE BY REAL-TIME ULTRASOUND SCANNING OF THE UTERUS

Transrectal real-time ultrasound scanning (5MHz linear array probe) examinations of the uterus were conducted to determine the accuracy of detecting pregnancy and nonpregnancy in 200 Holstein cows and heifers at 16 to 31 d following artificial insemination under field conditions. Two operators separately conducted the examinations. Overall diagnostic accuracy was 62.5%, with a sensitivity of 55.6%, specificity of 70.2%, and a positive predictive value of 67.8%. Diagnostic accuracy and sensitivity were lower (P < 0.05) for examinations performed early (16 to 22 d) than those performed at a later stage (23 to 31 d) after insemination. Diagnostic accuracy and sensitivity of the ultrasound examinations between Days 16 and 22 were 50.0 and 25.0%, respectively, and 70.2 and 68.8%, respectively, between Days 23 and 31. Between operators, no difference was noted in diagnostic accuracy, sensitivity, specificity, or predictive value. However, the sensitivity of one operator decreased slightly when his results were evaluated over three time periods. Results for the heifers examined were not different from those for the cows (P > 0.05) Determination of pregnancy and nonpregnancy, using ultrasound scanning examinations between Days 16 and 31 days postinsemination proved to be significantly less accurate than using palpation per rectum after Day 35 postinsemination. Palpation proved to be 99% accurate in diagnosing pregnancy when compared with breeding and calving records.