Ultrasonic characteristics of the uterus and ovaries during estrus, and their relationship with pregnancy rate in dairy cows

Sa？etak It was hypothesized that the accumulation of fluids in the uterine lumen reduces fertility in dairy cows. Therefore, the purpose of the present study was an evaluation of the ultrasound characteristics of the reproductive tract, including the accumulation of fluids in the uterine lumen during estrus, and the effect of these findings on pregnancy rates in dairy cows. The study was conducted on 486 lactating Holstein cows detected to be in estrous, on a large commercial dairy herd in Shiraz, Iran. Transrectal ultrasound was performed at the time of artificial insemination. Reproductive tract characteristics, comprising follicle diameters, the presence of corpus luteum in ovaries, the thickness, folding and edema of the uterus, and intrauterine fluid, were visualized and scored by ultrasonography. The cows were followed after insemination and their pregnancy rate determined. The effect of ultrasound findings were investigated in relation to pregnancy rates. The data were analyzed using logistic regression analyses. The results indicated that the pregnancy rate was significantly higher in cows with follicle size >14 mm (38.8%) compared with ≤14 mm (27.3%), after adjusting for the parity of the animals, days in milk and mean daily milk production (OR = 1.84, P = 0.005). No association between pregnancy rate and other ultrasound characteristics of the reproductive tract during estrus was observed in this study (P>0.05). In conclusion, follicle size is positively associated with the pregnancy rate of dairy cows in estrus. However, other ultrasound findings of the uterus, including intrauterine fluid, did not show any association with pregnancy rates