Qualitative characteristics of beef from Nellore, Angus and their crossbred fed whole shelled corn diets

Abstract

The objective of this study was to evaluate qualitative characteristics of beef from Nellore, Angus and their crossbreed fed whole shelled corn diets. Experiment 1: Seventeen Nellore and 17 Angus bulls with initial body weight of 381 ±12 kg were used in a completely randomized design using a 2 × 2 factorial arrangement (2 breeds and 2 diets). Experimental diets included: 1) a ground corn diet (GC) containing 30% corn silage and 70% GC and soybean meal-based concentrate, and 2) a whole shelled corn (WSC) diet containing 85% WSC and 15% of a soybean meal and mineral-based pelleted supplement. Twenty-four hours after slaughter, samples were taken from the longissimus thoracis muscle of the left half carcass between 12th and 13th ribs to analyze TBARS, color, cooking loss, shear force, myofibrillar fragmentation index, sarcomere length and fatty acid profile. Experiment 2: Sixteen Nellore and 16 Angus x Nellore steers with 353 ±25.3 kg were allotted in a completely randomized design using a 2 × 2 factorial arrangement (2 breeds and 2 diets). One diet contained 80% whole shelled corn and 20% of a protein-mineral pellet (WSC). The other diet had 74% whole shelled corn, 20% protein-mineral pellet, and 6% of bagasse sugarcane (WSCB). After slaughter, samples were taken from LT muscle of the left half carcass between 12th and 13th ribs for expression gene involved in lipid metabolism. Twenty-four hours after slaughter, samples were taken from the LT muscle to analyze chemical composition, color, myoglobin chemical forms, cooking loss, and shear force. In the Experiment 1, Angus beef was more tender compared to Nellore (P < 0.01). Angus bulls had greater concentration of polyunsaturated fatty acid (PUFA) and omega-6 (P < 0.01). Muscle of bulls fed WSC tended to have greater concentration of CLA C18:2 cis-9 trans-11 (P = 0.10), greater CLA C18:2 trans-10 cis-12 (P = 0.01) PUFA (P = 0.05), and consequently, greater oxidation. Regarding Experiment 2, there was no effect (P > 0.05) of breed and diet on chemical composition. Muscle from Nellore x Angus steers had greater expression levels (P < 0.05) of LPL, FASN and CPT2. There was a tendency (P = 0.10) of the beef from Nellore steers be lower tender than Nellore x Angus steers, before aging. Muscle from steers fed the WSC diet had greater expression of ACOX1 and grater lipid oxidation. In conclusion, Angus beef has greater marbling and tenderness, however Nellore and Nellore × Angus has similar marbling and tenderness after 14 days aging. Regarding diets, despite WSC diet not increases intramuscular fat, it has more PUFA that increase lipid oxidation.