This work was carried out to evaluate carcass characteristics, physicochemical and fatty acids compositions of Longissimus muscle from feedlot heifers fed cottonseed hulls (CSH) and soybean hulls (SBH) as forage, and different energy sources: ground corn (COR), corn germ meal (CGM) or whole rice meal (WRM). Twenty-four crossbred heifers (initial body weight of 350 ± 35 kg) were allocated in a completely randomized design into three treatments (diets) and eight replications (animals). Heifers were slaughtered after a 24-hour fasting period. Carcasses were identified, weighed and stored in a cold chamber at 2ºC until following morning in order to perform carcass evaluations. The animals fed the experimental diets did not differ as carcass characteristics, the average values for hot carcass dressing were 51.4%, the loin eye area, 50.8 cm², and fat thickness, 3.3 mm. The diets also did not influenced the physicochemical composition of Longissimus muscle, which showed 73.4% of moisture, 23.0% CP, 48.2 mg/100 g of cholesterol and 4.84 kgf/cm³ of shear force. Animals fed with CGM diet showed higher concentrations of CLA (0.48%), trans-vaccenic acid (7.69%) and worse omega 6/omega 3 ratio in the Longissimus muscle, due to the higher supply of linoleic acid provided by this diet as compared to the others. Animals fed WRM diet presented higher concentration of stearic acid in the Longissimus muscle, probably as a result of the higher content of oleic acid in this diet.
carcass characteristics; conjugated linoleic acid; fatty acid composition; shear force; trans-vaccenic acid
