Aim.

To compare the efficiency of the ultrasound and direct visual techniques for antral follicle counts, and the morphological characteristics of the ovaries of slaughtered heifers.

Methods:

A number of 102 ovary pairs from crossbred Holstein heifers collected postmortem were included. The study used the ultrasound and direct visual techniques to determine the size and weight of the ovaries, luteal body, and the number of <4 mm >4 mm antral follicles. A simple analysis of variance and the Tukey test at 5% were performed to compare the means of the variables pooled by phase of the estrus cycle and follicular wave. A two-way analysis of variance was performed to compare the two techniques and location of the ovarian structures (RO and LO). Additionally, the Pearson test was conducted to establish the correlation between the techniques.

Results:

The study found that the right ovary (RO) weighed 3.21 g more than the left ovary (LO). Besides, 86.27% of animals presented luteal body (LB) with a mean weight of 3.38 g. The size of ovaries, (LB), and > 4 mm antral follicle counts (AFC) performed through direct visual (Vis) and ultrasound (US) techniques were similar (P>0.05), with a high and significant correlation (r=0.75; P<0.001). However, the <4 mm AFC showed statistically significant differences (P<0.05) between the techniques, whereas the correlation was low and non-significant.

Conclusion:

Ultrasound is a highly efficient tool to assess > 4 mm ovarian structures. However, the correct determination of smaller structures will depend on other additional factors.