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

Subclinical endometritis (SCE) is a postpartum uterine disorder characterized by cytological inflammation without clinical signs, impairing fertility and productivity in dairy cattle. Diagnosis relies on endometrial cytology, which is invasive and impractical under field conditions. Doppler ultrasonography enables non-invasive assessment of uterine blood flow (UBF) and may detect inflammation-associated vascular changes. However, uterine hemodynamic characterization in indigenous Bos indicus breeds affected with SCE remains limited. This study evaluated Doppler-derived uterine perfusion dynamics in healthy and SCE-affected Tharparkar cows.

Twenty lactating multiparous Tharparkar cows (70 ± 3.34 days postpartum) were screened using endometrial cytology; cows with ≥5% polymorphonuclear cells were classified as SCE-positive (n = 10), and healthy cows served as controls (n = 10). Transrectal color and spectral Doppler examinations of the middle uterine artery (MUA) were performed every three days throughout one complete estrous cycle. Resistance index (RI), pulsatility index (PI), time-averaged maximum velocity (TAMV), blood flow volume (BFV), and MUA diameter were recorded. Serum progesterone (P₄) was measured by ELISA. Data were analyzed using independent t-tests, repeated-measures ANOVA (GLM), and Pearson correlation.

SCE cows exhibited significantly lower RI and PI across multiple cycle days (P < 0.05), indicating increased uterine perfusion. TAMV, BFV, and MUA diameter were significantly higher in SCE cows (P < 0.05). RI positively correlated with P₄ concentration (r = 0.77; P < 0.0001) and corpus luteum size (r = 0.64; P < 0.0001), while BFV showed positive correlations with TAMV (r = 0.82; P < 0.0001) and MUA diameter (r = 0.78; P < 0.0001), and negative correlations with RI (r = -0.57; P < 0.0001) and P₄ (r = -0.59; P < 0.0001). Production traits had no significant influence on Doppler indices (P > 0.05).

Subclinical endometritis in Tharparkar cows is associated with distinct uterine hemodynamic alterations characterized by increased blood flow and reduced Doppler resistance indices. These findings establish baseline Doppler reference patterns for an indigenous Bos indicus breed and support the potential utility of Doppler ultrasonography as a non-invasive adjunct tool for detecting uterine inflammation. Further studies integrating vascular and biochemical markers are warranted to enhance diagnostic precision.