Optical density changes in ultrasonographic images of the endometrium and corpus luteum in pregnant and cyclic cows

Optical density image (ODI) analysis, based on the intensity of pixels in digital images, is commonly used in orthopedic medicine. This study was conducted to quantify endometrial and luteal changes in early pregnant and cyclic cows by ODI analysis. Twenty healthy primiparous Simmental cows on days 80-120 postpartum were subjected to ultrasonography and ODI analysis on the days of estrus (day 0) and metestrus (day 4) as well as 12, 15, 18, and 21 days after insemination. The ODI values of pregnant (P) and nonpregnant (NP) cows were compared using two-way ANOVA. The P cows tended to have greater endometrial OD values than NP cows (772.2 vs. 740.5, P < 0.08), but their luteal OD values were similar (596.0 +/- 24). Both endometrial and luteal OD values varied over time in different patterns in P and NP cows in relation to gestational events until confirmation. In conclusion, preliminary data, especially endometrial OD values on day 15 relative to insemination, could have prognostic merit for a very early detection or confirmation of pregnancy. ODI analysis can be incorporated into ultrasonographic examination. However, more comprehensive experiments are needed to assure the prognostic value of ODI analysis.