316 EFFECT OF ULTRASOUND TRANSDUCER FREQUENCY ON FOLLICLE IDENTIFICATION ACCURACY IN CATTLE

Abstract

Ultrasoundsonography (US) is an essential tool for the study of reproductive physiology and is particularly useful in research on ovarian follicular dynamics in cattle. The resolution of the US images obtained, however, differs according to the frequency of the transducer used. The objective of this study was to investigate the effect of transducer frequency on the accuracy of follicle identification in cattle. A Honda HS-2000 sonograph equipped with 5.0, 7.5, and 10.0 MHz of B-mode linear rectal transducers was used in this study. A total of 22 ovaries with corpus luteum were collected from a local slaughterhouse. Each ovary was fixed on a paraffin block, immersed in de-gassed water, the transducer was placed at a distance of 1 cm from the surface, and sequential images from one end to other end of ovary were obtained at a distance of 1 mm. All follicles were aspirated by needle after imaging and were then injected with a pigment after counting by all frequencies. Subsequently, following freezing, 5-mm sections of ovaries were cut and the number of follicles in the sections was counted using a megascope. The follicles were classified into 4 groups according to their diameter: 2 to 3 mm, 4 to 6 mm, 7 to 10 mm, and 11 mm. The number of follicles observed using the megascope was compared with those observed at the 3 US frequencies. The ovaries were classified according to corpus luteum (CL) by determining the condition of the CL. Very red and small-sized CL (stage 1: ovary ovulated within 3 days), elastic and bigger CL (stage 2: ovary ovulated at 4 to 14 days), and regressed CL with yellow color (stage 3: ovary ovulated at 15 to 20 days). The data were analyzed by ANOVA. The results revealed no difference (P > 0.05) in the number of follicles observed in any size category using the US transducers and the megascope. Further, there were no differences between the different transducer frequencies and megascopic observations in terms of the number of follicles ≥4 mm in diameter. The stage of estrus in the ovary also had no effect on the number of follicles observed regardless of follicular size or the US frequency used. In conclusion, these results indicated that follicles could be counted accurately in excised ovaries using 5.0-, 7.5-, and 10.0-MHz transducers. Table 1.The average number of follicles in different frequencies and megascopic (n = 22)