Ultrasonography is a reproductive evaluation and biotechnology equipment commonly used in dairy farms. The ovaries receive the most blood flow compared to the rest of the organs of the reproductive tract so the assessment of the functional status of the ovaries and the corpus luteum (CL) allows to identify the reproductive status of open cows to implement reproductive strategies.
During its initial development the CL has a gradual increase in blood flow parallel with an increase in its volume and serum concentrations of progesterone. In addition, and during its regression phase, the CL size decreases at a lower rate than progesterone levels. The Color-Flow Doppler Ultrasound is currently used to monitor blood flow to the organs of the reproductive tract.
A recent study (Dubuc et al., 2020) showed that the use of the Color-Flow Doppler Ultrasound on the CL accurately identifies open dairy cows 21 days after artificial insemination (A.I.), the functional status of the CL and progesterone in blood.
This cohort study was performed on 10 herds and 1,632 Holstein cows which were subjected to an ovulation synchronization protocol during their first insemination.
At 21 days post A.I. the cows underwent examination of the ovaries by transrectal Color-Flow Doppler Ultrasound twice during that same palpation where the size of the CL was observed. They are classified by scoring coloration according to the color intensity on the CL surface as:
CL0: less than 10%
CL1: 11 to 30%
CL2: 31 to 60%
CL3 more than 61% coloration
In the case of a cystic CL, the surface used for analysis excluded the liquid-filled area. In addition, blood samples were taken to quantify progesterone using a sequential ELISA. Subsequently the cows were examined on day 32 post A.I. Cows with negative pregnancy diagnosis were subsequently synchronized according to the usual procedures of the farm.
The Color-Flow Doppler Ultrasound can be used to accurately diagnose pregnancy
Examination of the ovaries by transrectal Color-Flow Doppler Ultrasound 21 days post A.I. reported 22, 25.3, 35.2 and 17.5% of cows with a luteal body coloration of CL0, CL1, CL2 and CL3, respectively. The average CL size after A.I. was 22 mm and with 2.6 ng/mL average progesterone in blood.
The apparent prevalence of open cows 21 days after A.I. was 22 and 47% for categories CL0 and CL0+CL1, respectively. The precision measures to diagnose non-pregnancy using Color-Flow Doppler Ultrasound was high (99.0 and 94.8% for categories CL0 and CL0+CL1, respectively). If it is preferred to minimize the risk of diagnosing pregnant as non-pregnant cows, the category CL0 should be used, which has a specificity of 99% and a positive predictive value of 98%. The proportions of false negatives were 48.0, 26.4 and 0.7% for scores CL0, CL0+CL1 and CL0+CL1+CL2, respectively.
The CL size of less than 15 mm indicates an open cow, with the accuracy to diagnosis at 97. 5% (although the apparent prevalence was low, at 8%).
In conclusion, the Color-Flow Doppler Ultrasound can be used on CL to accurately diagnose pregnancy 21 days after A.I. It should also be noted however that this method is not necessary to confirm that a cow is pregnant.
Dubuc, J., Houle, J., Rousseau, M., Roy, J.P., Buczinski, S. 2020. Accuracy of corpus luteum color flow Doppler ultrasonography to diagnose nonpregnancy in dairy cows on day 21 after insemination. J. Dairy Sci. 103(2): 2019-2023.
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