Evaluation of three-dimensional sonography for antral follicle count in cycling dairy cows

The objective of the present study was to investigate reliability of transrectal three-dimensional ultrasound (3D-S) for antral follicle count (AFC) in dairy cows. Furthermore individual differences of AFC between cows and the fluctuation of AFC within and between different cycles were evaluated. To test the reliability of 3D-S, AFC was determined on the ovaries of 10 cows in vivo and compared with counts obtained after slaughter using computer tomography. To evaluate cyclic follicle dynamics, six cows were repeatedly examined with 3D-S over a period of two cycles. Using 3D-S, follicles with a mean diameter greater than 2 mm could be recorded. AFC determined with 3D-S and computer tomography showed a significant correlation (r >= 0.86, p < 0.05) and values were similar (p >= 0.05). AFC differed between individuals (p < 0.0001) and a moderate fluctuation within and between two cycles within the same cow was apparent (p < 0.05). In conclusion, 3D-S is a suitable method for determination of AFC in cattle. AFC differs between cows and cyclic fluctuations are apparent in a lesser extent.