Ultrasound scanning for carcass traits is a useful tool for obtaining valuable carcass information from a live animal. Ultrasound technology uses sound waves to develop images of body composition. Body composition traits that can be measured include 12th to 13th rib fat thickness, rump fat thickness, ribeye area, and intramuscular fat percentage (marbling). Each of these traits is at least moderately heritable and is significant in the determination of red meat quality and yield for individual animals.
Body Composition Traits
Rib Fat
Rib fat (also called fat thickness or backfat) is an external fat measurement taken between the 12th and 13th ribs. It is measured in inches. Rib fat is used in USDA yield grade calculation and is the most important determinant of retail yield. Higher amounts of rib fat decrease cutability and produce less desirable yield grades.
Ribeye Area
Ribeye area is the surface area of the longissimus dorsi (ribeye) muscle at the 12th rib interface on the beef forequarter. Ribeye area is expressed in square inches. Retail product yield increases and numerical yield grade decreases as ribeye area increases. This image is often the most difficult to collect and requires a highly skilled interpreting technician. Both rib fat and ribeye area are taken from the same image (Figure 1).
Figure 1. Ribeye area and rib fat image displayed on scanning equipment.
Rump Fat
Rump fat refers to the depth of fat at the juncture of the gluteus medius and superficial gluteus medius muscles. This measurement is expressed in inches. It is taken from an image collected between the hooks (hips) and pins of the animal. The rump fat measurement, together with the rib fat measurement, is used to determine more accurately the overall external body fat. This improves the accuracy of predicting percent retail product. In most cases, an animal will exhibit more fat over the rump than the rib, so often more variation is displayed in rump fat measurements than rib fat measurements. This image is highly repeatable and is the least difficult to collect or interpret. Rump images are required by some breed associations when submitting ultrasound measurements. Check with the breed association to determine if this is the case for a specific breed.
Intramuscular Fat
Intramuscular fat percentage (%IMF) is the percentage of fat in the ribeye muscle. It is often called marbling and is observed as flecks of fat in lean tissue. Degree of marbling is related to intramuscular fat percentage and is the primary factor determining quality grade (Table 1). Higher levels of intramuscular fat improve quality grade. This measurement should be collected when cattle are maintaining a high level of nutrition. The field technician collects four images (Figure 2), and the values generated by the interpreting software are averaged for an overall intramuscular fat percentage.
Figure 2. Intramuscular fat image displayed on scanning equipment.
Scanning locations on the live animal are illustrated in Figure 3. Intramuscular fat percentage is measured at position 1, ribeye area and rib fat thickness are measured at position 2, and rump fat thickness is measured at position 3.
Figure 3. Ultrasound scanning locations on the live animal.
Preparing for Scanning
Ensure a grounded electrical outlet is available for the scanning equipment, as generators are not preferred. Cattle must be dry, so covered holding facilities are necessary in case of rain. Severe weather may require postponing the scanning session. Provide supplemental heat for equipment if temperatures are low, and ensure cattle are kept out of direct sunlight during scanning for optimal image viewing.Cattle should be restrained in a squeeze chute during scanning, and they must be clipped to within half an inch and cleaned in the scanning area. Confirm with the technician if you need to supply clippers, extension cords, or other materials. Having an extra set of clippers is advisable.
Scanning and Image Processing
Record individual animal weights within 7 days of scanning, ideally at the time of scanning to minimize handling. If the scan weight is to be used as a yearling weight, it must be submitted accordingly. The technician will send images and completed barnsheets to an authorized lab for interpretation.Be aware of potential errors during processing, such as missing images or unpaid fees. If results are delayed, contact the technician or breed association for updates. Results will be communicated via email, mail, or member-specific screens.
Conclusion
Ultrasound scanning technology is a useful tool for collecting body composition data on live animals. The resulting data are less expensive and time consuming to collect compared with actual harvest data from beef carcasses. This technology allows seedstock producers to collect body composition data on prospective breeding animals for use in genetic improvement efforts. Ultrasound scanning results help breeders select cattle that best fit market specifications. This provides breeders with information for seedstock marketing as well.