Transrectal Spectral Doppler reveals uterine hyperemia in Tharparkar cows with subclinical endometritis

Subclinical endometritis (SCE) is an asymptomatic uterine inflammation that impairs fertility and is hard to detect in field conditions. We serially applied blinded transrectal spectral Doppler to characterize middle uterine artery hemodynamics across the estrous cycle in lactating Tharparkar cows with (n = 10) and without (n = 10) cytology-confirmed SCE. Doppler measures (resistance index [RI], pulsatility index [PI], timed-averaged maximum velocity [TMAX], blood-flow volume [BFV], artery diameter) and serum progesterone (P4) were recorded every 3 days from estrus through the next estrus. Repeated-measures analysis showed that SCE cows had consistently lower RI and PI and higher TMAX, BFV and artery diameter across the cycle (group effect P < 0.05). RI correlated positively with corpus luteum size (r = 0.64) and P4 (r = 0.77), while BFV correlated positively with TMAX (r = 0.82) and diameter (r = 0.78) and negatively with RI (r = − 0.57) and P4 (r = − 0.59) (all P < 0.0001). Limitations include modest sample size (n = 10/group) and absence of concurrent bacteriology or nitric-oxide measurements. With validation in larger cohorts, Doppler metrics could provide a non-invasive adjunct to cytology for detecting uterine inflammation and guiding reproductive management in tropical dairy systems.