Ultrasound Technology: Live Animal and Carcass Evaluation James R. Stouffer Cornell University, Ithaca, New York, U.S.A. INTRODUCTION Breeders, producers, packers, retailers, and researchers are becoming more concerned about carcass traits, as the livestock industry moves closer to the concept of value- based marketing. Animal scientists have desired the ability to determine the carcass traits of composition and quality in live animals as aids in selection of breeding stock and ideal marketing time for slaughter animals, to study the mechanism of growth and development, and to understand the effect of nutrition. This has led to the development of noninvasive objective evaluation methods including ultrasound. Early ultrasound equipment was large and had limited performance capabilities. Subse- quent developments have resulted in high-performance, durable, and lightweight ultrasound equipment that is associated with portable computers and sophisticated software. These systems produce rapid and accurate information for determining composition and quality characteristics of live animals and carcasses. PROPERTIES OF ULTRASOUND Ultrasound refers to high-frequency sound waves that are generated and received by a transducer associated with electronic equipment and, generally, a cathode ray screen. Ultrasound waves generated by the transducer are propagated through animal tissue until a slight change in density, such as tissue interfaces, will cause a portion of the ultrasound waves to be reflected back to the trans- ducer. These signals appear on a screen in proportion to time and therefore can be measured in terms of distance and tissue depth. EARLY EQUIPMENT The ultrasonic reflectance technique A-mode was used for the evaluation of fat thickness of swine [1] in the late 1950s. The ultrasonic equipment used in the early studies was metal flaw detection systems. Ultrasonic waves at frequencies of 1 to 3 MHz were used to detect tissue interfaces as well as flaws in metal. This equipment was also used to evaluate beef and lambs. Clipping of hair at the examination site and the application of motor oil as a couplant was required because of the limited performance of the equipment available at that time. Although the fat thickness was associated with a lot of the variation in composition, it soon became clear that the ability to measure lean depth and muscle area was required for increased accuracy. Subsequent studies [2] utilizing an improved technique were carried out on live market hogs and beef cattle. Depth readings of fat and muscle were made, starting at the backline and moving lateral at one-half-inch intervals and at recorded angles up to the lateral border of the rib eye muscle at specific desired rib locations on live hogs and cattle. These depth readings were then plotted on graph paper and the depths and muscle areas were plotted and measured. The A-mode scanning, plotting, and measuring on several groups of market hogs and beef cattle [3] demonstrated that this technique offered good potential, but it required much time and effort and was not practical. This encouraged the next generation of technology. A continuous mechanical scanning procedure was devel- oped, whereby a simulated B scan resulted from the movement of film across the signals originating from an A-mode unit in coordination with the movement of a single-element transducer on the animal. This technology was further developed and commercially marketed as the Scanogram in 1969. It was the primary ultrasonic system developed for evaluating animals that was marketed for the next decade. In order to produce a satisfactory image with the Scanogram, the animal had to remain still for approximately 10 seconds for a complete scan, and the film developed before the evaluation could be completed. ADVANCED TECHNOLOGY Real-time ultrasound represented a major breakthrough for noninvasive, objective animal evaluation. The medical Encyclopedia of Animal Science 853 DOI: 10.1081/E EAS 120019719 Copyright D 2005 by Marcel Dekker, Inc. All rights reserved. equipment industry developed ultrasonic systems that had multiple elements mounted in a linear array that could generate and receive signals from each element 15 30 times per second (i.e., real-time ultrasound). Linear array transducers of lengths up to 12.5 cm contained 64 100 elements, and a complete cross-sectional image could be produced in a fraction of a second and the frozen image viewed on the cathode ray tube of the ultrasonic unit. The real-time ultrasound equipment was used in the medical field for many diagnostic applications, and it became widely used in the livestock industry for evaluation of swine [4] and sheep although the transducer was too short to produce a complete cross-sectional image of beef cattle. A special transducer standoff guide was developed for use with the 12.5-cm transducer, which permitted the production and matching of two partial images. This technology was used for evaluating beef cattle. [5] The results were often inaccurate due to animal movement or poor operator technique. In 1990, an improved real- time ultrasonic scanner with a 17.2-cm linear transducer was developed and used for beef cattle. In 1991, this system was demonstrated for evaluating fat thickness, loin muscle area, and marbling score [6] on live cattle, sheep, and swine. Extensive reviews of the application of ultrasound for evaluation of live beef, sheep, and swine for the previous 30 years have demonstrated the extent of the previous research and the improvements that have been realized. Topics have included the application of ultrasound for feeding and finishing animals, [7] and for the selection of breeding stock [8] and the effect on genetic improvement. Ultrasound has been used for the selection of breeding hogs for more than 20 years. Images were interpreted visually by humans and measured manually with the aid of planimeters or computers. Results have shown that automation of the process for interpreting animal ul- trasonic images was feasible. CARCASS EVALUATION An automated evaluation system for determining fat depth and lean depth from longitudinal scans on freshly slaughtered and split pork carcasses was developed. [9] A 17.2-cm transducer mounted in a frame with a wedge- shaped standoff guide was used for longitudinally scanning pork carcasses from the tenth to last ribs two inches off and parallel to the backline. The 4°, wedge- shaped standoff guide prevented harmonic or ghost images that would have resulted in erroneous readings. The operator held the counterbalanced transducer in one hand while steadying the carcass with the other hand to ensure that the ultrasound beam from the transducer was correctly oriented (i.e., perpendicular to the desired tissue interfaces) to produce consistent, quality images. The automated depth measurements of fat and lean provided values as accurate for predicting percent carcass lean as careful manual measurements. These automated measure- ments were made at line speeds of 1200 carcasses per hour. This technology has been adopted and used in multiple commercial plants for more than 5 years. A similar version of this technology is being used by most of the major swine breeding companies in the world for the selection of breeding stock. As the performance of the ultrasonic equipment has improved in recent years, its use for determining marbling in the live animal has been developed utilizing sophisti- cated computers and software. Now it is common to see a complete portable system ultrasonic scanner, transducer, laptop computer, and a few accessories in use chuteside to evaluate live animals extensively. Marbling or intra- muscular fat is the most important factor associated with beef carcass grade, and it is associated with juiciness, flavor, and tenderness of the meat when consumed by the consumer. Quality is also receiving more attention in pork and lamb. The advent of real-time ultrasound provided a method of producing speckle patterns, which was subjectively evaluated by trained ultrasound operators. More recently, software programs have been devel- oped [10] that provide automated image grabbing and evaluation for marbling. CONCLUSION Ultrasound evaluation has advanced from the early equipment, which was bulky and had limited perform- ance, to portable ultrasound units with portable computers and sophisticated software capable of making rapid and accurate evaluations of live animals and carcasses. Currently, this technology is being used in commercial feedlots to determine the optimum time to market individual beef cattle in order to realize the maximum value. Evaluation of more than 100,000 beef breeding animals is being done each year. Pork carcass evaluation is being done on rapidly moving chain lines, and robotic automation has been tested and will soon be in use. Application of this technology for beef and lambs is anticipated in the near future. REFERENCES 1. Hazel, L.N.; Kline, E.A. Ultrasonic measurement of fatness in swine. J. Anim. Sci. 1959, 18, 815 819. 2. Stouffer, J.R.; Wallentine, M.V.; Wellington, G.W.; 854 Ultrasound Technology: Live Animal and Carcass Evaluation Diekmann, A. Development and application of ultrasonic methods for measuring fat thickness and rib eye area in cattle and hogs. J. Anim. Sci. 1961, 20, 758 767. 3. Stouffer, J.R.; Westervelt, R.G. A review of ultrasonic applications in animal science. J. Clin. Ultrasound 1977, 5, 124 128. 4. McLaren, D.G.; McKeith, F.M.; Novakoski, J. Predic tion of carcass characteristics at market weight from serial real time ultrasound measures of backfat and loin eye area in the growing pig. J. Anim. Sci. 1989, 67, 1657 1667. 5. Perkins, T.L.; Green, R.D.; Hamlin, K.E. Evaluation of ultrasonic estimates of carcass fat thickness and lon gissimus area in beef cattle. J. Anim. Sci. 1992, 70, 1002 1010. 6. Stouffer, J.R. Using Ultrasound to Objectively Evaluate Composition and Quality in Livestock. In Proceedings: 21st Century Concepts Important to Meat Animal Eval uation, University of Wisconsin, Madison, WI, Feb. 1991; Kaufmann, R.G., Ed.; Department of Animal Science: University of Wisconsin, Madison, WI, 1991; 49 54. Publication No. 285. 7. Houghton, P.L.; Turlington, L.M. Application of ultra sound for feeding and finishing animals, a review. J. Anim. Sci. 1992, 70, 930 941. 8. Wilson, D.E. Application of ultrasound for genetic improvement. J. Anim. Sci. 1992, 70, 973 983. 9. Liu, Y.; Stouffer, J.R. Pork carcass evaluation with an automated and computerized ultrasonic system. J. Anim. Sci. 1995, 73, 29 38. 10. Brethour, J.R. Estimating marbling score in live cattle from ultrasound images using pattern recognition and neural network procedures. J. Anim. Sci. 1994, 72, 1425 1432. 11. Stouffer, J.R. History of ultrasound in animal science. J. Ultrasound Med. 2004, 23, 577 584. Ultrasound Technology: Live Animal and Carcass Evaluation 855 . produce rapid and accurate information for determining composition and quality characteristics of live animals and carcasses. PROPERTIES OF ULTRASOUND Ultrasound refers to high-frequency sound. cattle from ultrasound images using pattern recognition and neural network procedures. J. Anim. Sci. 1994, 72, 1425 1432. 11. Stouffer, J.R. History of ultrasound in animal science. J. Ultrasound Med evaluation could be completed. ADVANCED TECHNOLOGY Real-time ultrasound represented a major breakthrough for noninvasive, objective animal evaluation. The medical Encyclopedia of Animal Science