The objective was to determine the accuracy of color Doppler ultrasound for diagnosis of early pregnancy in buffaloes based on the evaluation of corpus luteum blood flow (CLBF) on days 20 and 21 after mating. Local Egyptian
buffaloes, (n=12) during 3rd and 4th lactational season were kept in the farm of Animal Reproduction Research Institute (ARRI). The animals were divided into two groups, group A (n=6) was mated naturally by a fertile bull during late estrus
phase and group B (n=6) was left. Animals underwent grayscale ultrasonography (US) to locate the CL , then color flow Doppler and power Doppler were activated to evaluate CLBF and pulsed wave Doppler to evaluate uterine blood flow on days 1,5,10,12,14,16,18,19,20,21,23,25,27,30 after mating, using a portable, battery operated color Doppler and B-mode ultrasound scanner equipped with a 10-5MHz, rectal transducer (M-turbo, Fujifilm sonosite, USA). Based on subjective (visual) and objective (Doppler parameters) corpus luteum blood flow (CLBF) evaluation. Animals in group A were classified as pregnant or non- pregnant on day 20 and day 21 after mating depending on CLBF. Blinded from results of the previous diagnosis, we performed a final pregnancy diagnosis using US to visualize the fetal heartbeat
on day 30 after mating. Blood samples were collected from jugular vein after examination to determine by ELIZA kits, serum estradiol and progesterone concentration. The final pregnancy outcome on day 30 was retrospectively
compared with the CLBF on days 20 and 21 diagnoses and then classified as true positive, true negative, false positive, and false negative. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the CLBF-d20-21 test were calculated using specific equations. The CLBF decreased markedly on days 20-21 in case of non-mated group < br />(CL regression), while it remained constant or slightly increased in case of pregnant animals. Moreover the uterine blood flow markedly increased in case of non-mated group during the same period.