Endometrial echogenicity at insemination is associated with conception in primiparous Holstein cows

Echotexture analysis of the bovine endometrium has been used to detect established pregnancy. It was asked instead whether echotexture at insemination is associated with that service's outcome. Forty-nine inseminations in 34 primiparous Holstein cows, free of endometritis and bred to one sire between Days 90 and 150 postpartum, were imaged transrectally on Days 0, 4, 12, 16, 18 and 21. Mean grey level (MGL), homogeneity and contrast were computed from the images. Pregnancy was confirmed on Day 35; 33 services succeeded and 16 did not. With cow as a random effect and service nested within cow, MGL was 9.84 units higher in services that succeeded (P = 0.001), and 10.01 units higher among first services alone (P < 0.001). Contrast differed in the same direction (P = 0.011) and homogeneity did not (P = 0.065). Neither measurement day nor its interaction with outcome was significant, and the difference was 14.3 units at insemination (P = 0.003). Discrimination was best on that day (area under the curve 0.755, 95% CI 0.61-0.90). In the 12 cows bred both unsuccessfully and successfully, each her own control, MGL was 9.86 units higher at the successful service (P < 0.001). Endometrial echogenicity is therefore better explained as a condition of the uterus at each service than as a fixed property of the cow. Because the reading is available before breeding, the finding identifies a candidate marker of uterine condition at service rather than a pregnancy test, and one needing validation in an independent cohort.