Ultrasound found its first applications in livestock research in the 1950's.  Since that time, great strides have been made in ultrasound research that have benefited both human medicine and the livestock industry. Most people probably associate ultrasound with human fetal examination. In human medicine, it is most commonly used in routine pregnancy exams and sex determination. This same technology and even identical equipment is used in the beef cattle industry to evaluate reproductive and carcass characteristics.
 
 

What is ultrasound?   Technically, ultrasound is mechanical pressure waves, or sound waves, with frequencies above 20,000 Hz (oscillations per second).  The portion of an ultrasound unit that actually emits and receives sound waves is known as a transducer.  As sound waves are emitted from the transducer and pass through different tissues with different densities, signals are produced that detect this density change and are passed back to the transducer.  For example, muscle and fat have different densities thus allowing for their differentiation. "Real-time" ultrasound is most commonly used in the industry, although other ultrasound technologies are being investigated. Simply put, real-time ultrasound allows the operator to view the image in "real time".
 
 

 Ultrasound data is useful in identifying animals that are superior or inferior for a particular trait of interest.  Collecting ultrasound data is also a much cheaper and more efficient means of evaluating carcass traits on breeding animals relative to progeny testing and carcass data collection.

For ultrasound measurements to be useful in measuring fat thickness, ribeye area, rump fat and percentage of intramuscular fat, they must be accurate, precise and repeatable. Accuracy is the ability of a technique to rank the measurements correctly.   Precision implies correct ranking and that the measurements taken were the same as some objective comparison.  Useful measurements should also be repeatable.  For example, if a group of cattle were measured ultrasonically one day, would the same measurement result if done the next day?  If producers are using experienced well-trained ultrasound technicians, the answer should be yes.  For measuring back fat and ribeye area, research clearly indicates that when using qualified technicians, ultrasound can be a useful tool for gathering carcass information in live cattle.  Recently, the Beef Improvement Federation has sponsored annual ultrasound certification programs. In order to be certified, technicians must pass accuracy, precision, and repeatability tests for 12-13th fat thickness and ribeye area. Also, a written examination is given.