Invited Review: Use of ultrasonography to make reproductive management decisions1,2

Transrectal ultrasonography has been available for making reproductive management decisions since the mid 1980s. This technology allows for the real-time visualization of internal structures (i.e., ovary and fetus) that are otherwise difficult to evaluate. The use of this technology in making reproductive management decisions can be divided into 3 key areas: (1) selection of animals to be kept in the breeding herd, (2) increasing the likelihood of reproductive success, and (3) pregnancy determination. When selecting replacement animals, ultrasonography can be used to assess antral follicle counts in females. Antral follicle counts have a direct effect on animal fertility. Prior to the start of the breeding season, transrectal ultrasonography can be used to determine puberty status, reproductive tract score, and estrous cycling status. In addition it can be used to determine response to synchronization protocols (presence of a dominant follicle, ovarian cyst, and follicle diameter), or if other assisted reproductive technologies are being used, it can be used to predict success (superovulation response or presence of a corpus luteum for embryo transfer). Following insemination this technology can be used to determine pregnancy status as early as 28 d after insemination, fetal age and sex, and presence of multiple offspring. The largest limitations to the use of ultrasonography include the time and technical skills required, strain on the arm and shoulder, and cost of equipment. Whereas probe handles can be used for pregnancy diagnosis exams, measurements on the ovary require consistent placement of the transducer that to date can only be accomplished manually. Future improvements that may overcome some of these limitations include better imaging software, larger hard drives allowing the storage of video clips, and improved diagnostic capabilities of the machine (i.e., software that will be able to use pixel density to categorize ovaries). Color Doppler and 3-dimensional images are being explored for earlier pregnancy diagnosis and for blood flow and health of the corpus luteum and follicles. Thus, transrectal ultrasonography has and will have a role in the successful reproductive management of cattle herds.