Reproductive Applications of Ultrasound in the Cow

Abstract

During the past decade portable ultrasound units that provide excellent image quality have become available to veterinary practitioners. The use of transrectal ultrasonography for evaluation of reproductive structures in cattle extends and enhances the diagnostic capabilities of practitioners beyond the traditional use of palpation per rectum. Ultrasonography of ovaries enables more consistent differentiation of ovarian follicles and corpora lutea. Accurate counting of follicles and precise measurement of follicles or corpora lutea is possible. Sequential monitoring of ovarian structures enables the user to characterize ovarian follicular waves, to identify dominant follicles and to detect ovulation. Images can be used to identify, objectively measure and to characterize the quality of a corpus luteum. Ultrasonography is also a valuable tool for identification of abnormal (cystic) luteal and follicular structures. Pregnancy diagnosis can be performed using ultrasound by day 19 to 24 post-breeding and fetal viability can be verified by visualization of a fetal heartbeat. Aging embryos and fetuses between days 20 and 100 of gestation can be facilitated by measuring crown-rump length (20-50 days) or the diameter of the head or trunk (50- 100 days). Sexing of bovine fetuses is accomplished by visualizing the genital tubercle (penis) and scrotum in males or by the lack of male genetalia and the presence of the genital tubercle (vulva) in females. Sex determination is most practical between days 60 and 85 of gestation. Like other diagnostic tools, ultrasound has limitations. Skill of the ultrasound technician in capturing clear images, differentiating anatomical orientations and interpreting ultrasound images is essential. The effective use of ultrasound technology enhances diagnostic capabilities and increases the services offered by veterinarians.