Spectral Doppler Ultrasound in selecting an equine embryo receiver.

The aim of this study was to evaluate if the RI and PI values ​​would help in choosing the best embryo recipient, and observe whether CL vascularization would influence P4 production. The study was conducted the breeding season 2018/2019 utilized 35 mares were used for data collect referent the variables the project on the day of embryo transfer. The mares were divided into five groups according to the day after ovulation with D0 being the day of ovulation. Thus, the groups were divided into: D4 - mares that were on the 4th post-ovulation day; D5 - mares that were on the 5th post-ovulation day; and so successively for D6; D7 and D8. On the day of embryo transfer, the CL of the mares selected as recipients was evaluated by B mode and Power Flow mode ultrasonography and the right and left dorsal branches of the uterine arteries by spectral mode ultrasonography. Blood samples were taken on the day of the embryo transfer for dosage of P4 concentration by radioimmunoassay. No statistical difference was found between the variables when the mares were separated into pregnant and non-pregnant mares, nor when they were separated by age groups. When compared the groups by day of embryo transfer was found statistical difference in RI variable between the groups D5 X D6 (p = .0053) and D6 X D8 (p = .0036). Ever in PI variable the statistical difference found was between groups D4 x D8 (p = .049); D5 X D6 (p = .0446) and D6 X D8 (p = .0024). We conclude that mares with RI measurement of uterine arteries near 1.0 are correlated to mares with high CL vascularization and elevated P4 concentration.