The Utility of Ultrasonic Measurements in Growing Swine

Ultrasonic backfat depth and longissimus muscle area measurements were obtained on live swine in five weight groups ranging from about 25 to 90 kg. These measurements were compared with traditional measurements obtained on the vertically hanging carcass of the same animal. The carcass and ultrasonic measurements did not always agree in absolute terms, but, for the most part, the same relationship was obtained between the two in all weight classes. Ultrasonic measurements were as well correlated as corresponding carcass measurements with several indicators of body composition, regardless of weight group. Ultrasonic techniques readily monitor short-term changes in swine backfat thickness and longissimus area during growth. In pigs started at about 20 kg body weight, ultrasonically detectable changes in backfat depth or longissimus area were observed after 1 or 2 wk. The changes in individual backfat layers were quantified by ultrasonic measurements in growing pigs. This nondestructive technique using sequential measurements on the same animal appears particularly useful for measurement of growth or body composition in experiments in which animals are manipulated nutritionally or otherwise.