Use of B–mode and Power Doppler ultrasonography of the uterus and preovulatory follicle to predict ovulation time in Holstein cows after heat synchronization

Aim of study: To evaluate the utility of B-mode and Power Doppler ultrasonography to predict ovulation time in Holstein cows by assessment of uterine and follicle measurements. Area of study: Galicia, NW Spain Material and methods: 33 Holstein cows were examined every 12 h until ovulation. Measurements for the ratio endometrium/myometrium (END/MYO), uterine lumen (UL), diameter of the dominant follicle (DF), and Power Doppler of the dominant follicle and corpus luteum were recorded. The times of onset of heat, maximum heat (MHA) and heat finalization were obtained from the database of monitoring devices. Blood samples were taken at each examination for progesterone (P4) determination. Data were analyzed using one-way ANOVA and Pearson’s χ2 tests. Main results: For UL, time -6 (1.53 mm) with respect to ovulation (time 0) significantly differed from time -42 (5.70 mm). Concerning DF, significant differences were observed between time -6 (20.48 mm) and time -54 (16.60 mm). As for P4, significant differences were found between time -6 (0.34 ng/mL) and time -54 (1.03 ng/mL). Considering MHA, significant differences were observed for the UL between after and before/during groups; for DF, significant differences were found before and after MHA. As for heat, the UL significantly differed between after and before/during groups. Significant differences were found for the percentage of cows with Doppler signal in the ovulatory follicle and corpus luteum concerning MHA and heat factors. Research highlights: The use of Power Doppler to predict ovulation time needs to be refined. The END/MYO and UL measurements could be useful to identify cows in heat, but inaccurate to determine ovulation.