The relationships of ultrasonic estimates of fat thickness and l. dorsi to selected carcass traits of steers and heifers

The use of ultrasonics in estimating muscling and fatness in live animals is a comparatively new technique. Favorable results in previous experiments have indicated a potential use in the livestock industry. The principal use of ultrasonics, if successfully developed, would be for the selection of breeding animals. It would assist breeders to select those breeding animals which possess a higher proportion of lean in the carcass. Previously, the basis for selecting breeding animals which have superior carcasses, has required carcass evaluation of the offspring of sires and dams which have been selected for type and rapidity and efficiency of weight gains. Due to the long generation interval in cattle, evaluating sires for carcass traits has proved to be a costly process. Many breeders have disposed of a sire before his potential value to the herd, in terms of carcass traits, was known. Ultrasonics may enable breeders to eliminate years of experimental breeding for leanness by being able to evaluate the carcass potential of an animal before it is placed in service. The purpose of this study was to compare ultrasonic estimates of ribeye area and fat thickness in steers and heifers with the actual carcass values, using interpretations of the somagrams by three different experimenters and an average of the three.