August 20, 2010
Ultrasound machines use sound waves to create images viewed on a screen. The sound waves are not audible by human ears but are instead detected by specialized crystals in a probe. A computer translates the information into an image viewed live or captured to be viewed at a later time. Early ultrasound machines produced a grainy image but technology continues to improve. Some of the most sophisticated ultrasound machines are able to translate the reverberated waves into three-dimensional images.
Uses of ultrasound machines in veterinary medicine continue to expand. Operators use specialized probes to view and measure abdominal organs, view internal structures of the eye, evaluate musculoskeletal injuries, estimate carcass characteristics and many others. Some cow-calf veterinarians are busy this time of year using ultrasound to determine pregnancy status.
Ultrasound is an accurate definitive means to evaluate the reproductive tract of a cow. Structures on the ovaries can be viewed. Follicles can be counted, measured and tracked through time with repeated scans. Cystic structures can be observed and treated to maintain normal reproductive cycles. Pockets of abnormal uterine fluid and uterine infections can be diagnosed. Most commonly, however, cow-calf veterinarians use ultrasound to determine pregnancy status.
Ultrasound can be used to visualize a developing fetus after thirty days of gestation. Measurements of the fetal head, body and length can be used to determine the length of gestation to within a couple of days. However, around one hundred days of gestation the growing fetus begins to fall beyond the depth obtainable by the ultrasound. At this point parts of the fetus and/or fetal membranes are visible but the veterinarian is unable to stage gestation with ultrasound.
Though ultrasound is very useful when determining the stage of early gestation, variation in the length of gestation between individuals makes determining the calving date much more difficult. In fact, two females bred on the same day can calve more than two weeks apart. Twins are more easily detected earlier in gestation when the smaller fetuses can be viewed at the same time. From about day 65 to day 100 the sex of the fetus can be determined. The presence of a vulva, scrotum, and/or sheath is used to determine the sex of the growing calf.
Ultrasound provides a great deal of information for the rancher. Data obtain can be used to mark and sort cattle into calving groups. Producers can determine females bred via artificial insemination. Females can be marketed as producing bulls or heifers. Pregnancy status can be determined earlier to market open heifers with the peak yearling market. Open cows can be sold earlier in times of feed shortage or to take advantage of peak cull prices.
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Though ultrasound provides a great deal of useful information it is not applicable to all producers. In order to be justified, the information needs to be directly applied into management considerations. For example, sorting cows into calving groups can be very helpful to the rancher that calves in a short period of time, in somewhat tight area, or has a greater incidence of calving difficulty. That management scenario contrasts greatly from the herd that calves over 90-plus days on range with very little oversight. Ask your veterinarian how advanced diagnostics and technology can be helpful to your ranching operation.