This study will be carried out to evaluate diets containing 80% concentrate on dry matter (DM) and different levels of linseed oil, rich in polyunsaturated fatty acids (1%, 3.8% and 5.2% in DM ), for finishing crossbred cattle on feedlot, and its influence on diet intake, performance, carcass characteristics, meat quality and muscle fibers. Thirty crossbred Nelore x Canchim, 15 castrated males, weighing 380 kg and 24 months of age and 15 females, with 360 kg and 24 months of age. These animals will be confined in individual pens for 112 days (4 sub-periods of 28 days) after 21 days of adaptation to the diets and facilities management. The exclusive roughage will be sugar cane variety IAC 86-2480. The diets will be offered twice a day, allowing 10% leftover. The intake assessment and control of food intake will be conducted. The weight of the animals will be held at the beginning and every 28 days until the end of the experiment, preceded by fasting of solid and liquid for 15 hours. Body measurements for assessment of animals' development and ultrasound images for muscle growth and fat deposition evaluation will be obtained in the first and last day of the experimental period. At the end of the feedlot, the animals will be sent to a commercial slaughterhouse and slaughtered in accordance with usual procedures of the establishment. The assessment of carcass traits will be done by weighting of hot and cold carcass, carcass length and width, loin eye area, fat thickness, pH, temperature, proportion of forequarter, ribs and hindquarter, weight and yield of retail cuts from the hindquarter. After cooling, samples of Triceps brachii and sections of loin (Longisimus) between the 9th and 13th ribs will be removed from the left carcass for assessment of meat quality, which comprise: pH, meat and fat color, holding water capacity, cooking losses, shear force, muscle fiber composition, total and soluble collagen, composition and relationship between fatty acids. A completely randomized factorial 3 x 2 (oil level x sex condition) with five replications will be used for statistical analysis.
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