The evaluation of corpus luteum blood flow using color-flow Doppler ultrasound for early pregnancy diagnosis in bovine embryo recipients

The objective of this experiment was to evaluate corpus luteum blood flow (CLBF) as an early indicator of pregnancy status in bovine embryo recipients. Fifty crossbred beef cows were submitted to embryo transfer on Day 7 after estrus. On Days 7, 11, 13, 15, 17, 19, 21, 26, 33, and 40, a blood sample was taken, the CL examined using a color-flow Doppler ultrasound scanner, and video was recorded of each scanning session. Ultrasound data were grouped by the first day progesterone concentrations were <1 ng/mL (indicating early embryo loss, EEL) through Day 21 (EEL-17, n = 3; EEL-19, n = 9; EEL-21, n = 3), absence of an embryo on Days 26, 33, or 40 (late embryo loss; LEL; n = 12), or remained pregnant (P; n = 23). The first decrease in CLBF of EEL-17, EEL-19, and EEL-21 cows compared to P cows occurred on Days 17, 19, and 21, respectively (P < 0.05). There was no difference in CLBF between LEL and P cows on Days 17, 19, and 21. Six evaluators diagnosed pregnancy from randomized video clips on Days 17, 19, and 21. Evaluators made more (P < 0.004) correct diagnoses on Day 19 than Day 17. Sensitivity (82.9 ± 10.1%) was not affected by day. From Days 17 to 19, diagnostic specificity increased (P = 0.046) from 43.2 ± 3.0 to 54.3 ± 3.0% but remained unchanged thereafter. Due to low specificity and sensitivity, evaluation of CLBF alone was insufficient for early pregnancy diagnosis.