Ultrasound scanning (Auskey System, Animal Ultrasound Services, Inc., Ithaca, NY), using an average of three measurements taken from a 7.5 cm longitudinal scan anterior to the last rib and 5.5 cm off of the midline, was used to measure backfat and loin depth at each weigh period. These data were then used to predict carcass lean content using equations from Cisneros et al. (1996); carcass lean content was used to calculate lean growth rate.