Sixteen Nellore and Sixteen Nellore × Angus steers with an initial body weight of 353 kg ±25.3 kg were randomly assigned into 2 feeding groups: whole shelled corn without forage (WSC) or WSC with sugarcane bagasse (WSCB), to evaluate muscle chemical composition, expression of genes involved in lipid metabolism, and other beef quality attributes. The first diet has 80% whole shelled corn and 20% soybean meal, and a mineral supplement (WSC). In the WSCB, 6% of corn was replaced by sugarcane bagasse. The experiment had a completely randomized design in a 2 × 2 factorial arrangement. Gene expression was analyzed using RT-qPCR. There was no effect ( P > 0.05) of breed and diet on muscle chemical composition. There was a tendency ( P = 0.10) for Nellore beef to be less tender, only 3 days after slaughter. Muscle from Nellore × Angus had higher expression ( P < 0.05) of LPL , FASN, and CPT2 , than in the muscle of Nellore steers . Muscle from steers fed WSC diet had higher expression of ACOX1 and lipid oxidation ( P < 0.05). SREBF1 gene was expressed lower ( P < 0.01) than PPARA and PPARG in the muscles of all steers. It is possible to conclude that Nellore × Angus greater expression of lipogenic and lipolytic genes, which impair intramuscular fat deposition. Moreover, the use of bagasse in a WSC diet did not upregulate SREBF1 and other lipogenic genes expression, as well as did not increase intramuscular fat.
Teixeira et al. (Sun,) studied this question.