Ultrasound rib eye area
Accurate live animal, ultrasound measurement of ribeye area is dependent on three major items: clear and distinct medial and lateral end borders, not being over any portion of 12th or 13th rib, and good transducer-animal contact. The presence of well-defined intercostal muscles under the longissimus dorsi is an indication that the transducer is properly aligned directly between the 12th and 13th ribs for this measurement. Ultrasound technicians and image processing labs should be certified or accredited by the Ultrasound Guidelines Council (UGC). The UGC standards for certification can be found at https://ultrasoundguidelinescouncil.org/wp-content/uploads/2021/09/UGC-SG-VII-FC.pdf.
Ultrasonic ribeye area is adjusted to a common age (e.g., 365 days of age), and in multiple-breed settings is also adjusted for breed composition and heterosis.
Animals of the same sex, reared and managed together up until the time of scanning, form a contemporary group. Scanning contemporary group definition includes the following: herd code, weaning date, weaning management group (pasture, creep, non-creep, etc.), scanning date, and post-weaning management group designation. For animals scanned at a central test, the contemporary group definition for an animal should include its herd of origin and other birth and weaning contemporary group information.
Given the ultrasound measure of ribeye area is an indicator of the economically relevant trait of carcass ribeye area, it is generally included in multiple-trait models that include carcass ribeye area and potentially other traits such as carcass weight. There are no maternal effects fitted for ultrasound or carcass traits given the maternal influence declines post-weaning.
Ultrasound ribeye area is an indicator trait that is measured on seedstock animals. It is used to help predict the genetic merit of animals for carcass ribeye area. The majority of beef breed organizations do not publish an ultrasound ribeye area EPD but rather publish an EPD for carcass ribeye that is the product of a multiple-trait model including the ultrasound indicator trait.