Kazama et al., 2008. Rev. Bras. Zootec., 37 (2): 350-357

This study was carried out to evaluate the carcass characteristics, physicochemical and fatty acid compositions of longissimus muscle from feedlot heifers fed cottonseed hulls (CSH) and soyabean hulls (SBH) as forages and different energy sources: ground maize (COR); maize germ meal (CGM); or whole rice meal (WRM). 24 crossbred heifers (initial body weight of 35035 kg) were allocated in a completely randomized design into 3 treatments (diets) and 8 replications (animals). The heifers were slaughtered after a 24-h fasting period. Carcasses were identified, weighed and stored in a cold chamber at 2°C until the following morning in order to perform carcass evaluations. The animals fed the experimental diets did not differ in carcass characteristics. The average values for hot carcass dressing, loin aye area and fat thickness were 51.4%, 50.8 cm 2 and 3.3 mm, respectively. The diets also did not influence 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/cm 3 of shear force. Animals fed with CGM diet showed higher concentrations of CLA (0.48%), trans-vaccenic acid (7.69%) and lower omega 6/omega 3 ratio in the longissimus muscle, due to the higher supply of linoleic acid provided by this diet compared to the others. Animals fed WRM diet presented a higher concentration of stearic acid in the longissimus muscle, probably as a result of the higher content of oleic acid in this diet.