MadozLV_Detection of early pregnancy and embryo losses by color Doppler ultrasound and interferon-stimulated genes expression in grazing dairy cows
Whereas in confinement housed cattle, numerous studies have been performed to describe pregnancy losses between 19 and 34 d post-AI, little is known about embryo mortality in grazing dairy cows. The objectives of this study were 1) to assess the diagnostic value of the CL blood flow (CL-BF) evaluation by Doppler ultrasound (US) to detect non-pregnant cows at 19-20 d post-AI compared with the interferon-stimulated genes (ISG) mRNA expression, and 2) to assess the rate of embryo mortality between 19 to 34 d post-AI. The luteal blood flow of all cows included in the study (n=131) was examined on-farm by Power and Color mode of Doppler-US and later using an image processing software by a second evaluator. The endometrium thickness and echotexture were evaluated by B-mode US at the same visit to assess if pregnancy diagnosis can be improved at 19-20 d post-AI by this additional diagnostic tool. Blood samples were obtained at 19-20 d post-AI for progesterone measurement by chemiluminescence and to determine the mRNA expression of ISG by real-time PCR. Pregnancy diagnosis based on embryo visualization was performed at 33-34 d post-AI by ultrasound B-mode. At 19-20 d post-AI, the pregnancy rate was 58.7% diagnosed by Doppler-US and 62.7% diagnosed by ISG mRNA expression in leukocytes, while at 33-34 d, it was 37.4% diagnosed by B-mode US. Based on these results, we found that 31.3% of the cows pregnant by Doppler ultrasound and ISG mRNA expression in leukocytes at 19-20 d experienced embryo loss and were non-pregnant at 33-34 d post-AI. In parallel interpretation, ISG15 and MX2 mRNA expression in leukocytes were regarded as suitable biomarkers for early pregnancy and were selected for molecular characterization of pregnancy at 19-20 d post-AI. The Doppler ultrasound’s color mode showed similar accuracy and a higher negative predictive value as the genes selected as biomarkers. The additional B-mode ultrasound evaluation of the uterine stratum vasculare and the endometrium thickness improved the diagnostic accuracy. Therefore, assessing the corpus luteum blood flow by Doppler-US allowed detecting early and quickly non-pregnant cows at 19-20 d post-AI; and performing pregnancy diagnosis by the B-mode US at 33-34 d allowed detecting pregnancy losses. This combination could be a useful, practical application for, e.g., resynchronization protocols in veterinary dairy practice.