PSV-33 Marbling and expression of genes involved in lipid metabolism in the muscle of Nellore and Nellore × Angus steers fed whole shelled corn diets

Abstract

Abstract The objective was to evaluate marbling and the expression of genes involved in lipid metabolism in the muscle of Nellore and Nellore × Angus steers fed whole shelled corn (WSC) diets. Thirty-two steers with initial average body weight of 353 ±25.3 kg were used in a completely randomized design using a 2 × 2 factorial design (2 breeds and 2 diets). One diet had 80% of WSC and 20% of a soybean meal and mineral-based supplement. The other diet had 74% of WSC, 20% of the same supplement, and 6% of sugarcane bagasse. Immediately after the slaughter of steers (around 450 kg of body weight), longissimus thoracis (LT) muscle samples were collected, frozen in liquid nitrogen, and stored at −80°C for gene expression analyses using RT-qPCR. Twenty-four hours after slaughter, samples were taken from LT muscle to analyze marbling score. The model included breed, diet, and their interaction as fixed effects and animals as random effect. There was no effect of breed (364 and 358; P = 0.80) and diet (355 and 367; P = 0.56) on LT marbling. Nellore × Angus steers had greater expression of LPL, FASN, and CPT2 (Table 1), which means a greater lipid turnover. The expression of SCD1 gene tended to increase (P = 0.06) in muscle of Nellore steers fed WSCB diet, while in Nellore × Angus muscle, this diet tended to decreased SCD1 expression. Regarding diet, steers fed WSC had lower expression of FABP4, and greater expression of ACOX1. In conclusion, Nellore × Angus had greater fatty acid uptake, synthesis, and oxidation that did not result in greater intramuscular fat. In addition, animals fed whole shelled corn diet with sugarcane bagasse did not increase expression of SREBF1 and lipogenic genes, and consequently did not increase marbling. Funded by Capes, Fapemig and INCT-Ciência Animal.