The objective ofthis trial was to evaluate carcass traits of 56 bulls from three genetics groupsaveraging 18 months of age and receiving two feeding levels. Twelve bulls wereslaughtered in the beginning of the study and used as reference animals. Theremaining 16 genetically improved Nellore, 12 ordinary Nellore, and 16 geneticallyimproved Caracu averaging 404, 345, and 434 kg of initial body weight, respectively,were randomly assigned to a completely randomized designed with a 2 x 3 factorialarrangement (two dietary levels and three genetic groups). Intake was eitherrestricted to 65 g DM/ kg BW0.75 per day or ad libitum. Corn silage wasused as the forage component of the diet while ground corn, cottonseed meal,urea, monensin, and a mineral mixture as the concentrate portion of the rationyielding a forage:concentrate ratio of 50:50. The slaughter weight was determinedby ultrasound when animals reached an average of 4 mm of subcutaneous fat. Significantfeeding regime x genetic group interaction was observed only for percentageof bone tissue. Carcass weight and depth and weights of fore and hindquartersdid not differ comparing the genetically improved breeds but were lower forordinary Nellore. The highest hindquarter yield was observed for animals fedad libitum. Dressing percentage was not affected by feeding regime andwas higher on Nellore groups; hindquarter percentage also was higher on Zebuanimals. Both subcutaneous fat thickness and percentage of adipose tissue weregreater for ordinary Nellore while loin eye area and percentage of muscle tissuewere higher for Caracu.
