NÍVEIS DE FDN EM DIETAS DE TOURINHOS NELORE TERMINADOS EM CONFINAMENTO

MEDEIROS, C.F. Levels of neutral detergent-insoluble fiber in the diets of nelore bulls finished in confinement 41f. Dissertation (Master's) - Faculty of Veterinary Medicine and Animal Science, Federal University of Mato Grosso do Sul, Campo Grande, MS, 2023. The experiment was carried out to evaluate the effect of different levels of fiber in the diet of young bulls finished in confinement on animal performance and production cost. For this, 20 non-castrated male Nellore cattle aged 30 months were distributed in a completely randomized design and individual stalls in four treatments with 25%, 30%, 35%, and 40% NDF content in dry matter. The variables of final live weight, average daily gain, dry matter intake, and feed conversion were evaluated. At the end of the experiment, the animals were transported after fasting for 12 hours and slaughtered in a commercial slaughterhouse, where the weight of the hot carcass and the hot carcass yield were determined. The effect of the NDF level on consumption results was observed, with maximum estimates between 28 and 32% NDF. Productive performance was affected by the NDF level. The variables final BW, total weight gain (TWG), average daily gain (ADG), hot carcass weight (HCW), and carcass yield (CY) showed quadratic behavior (P<0.05). The maximum points for final BW, HCW, and ADG were 29.9%; 29.6%, and 25% of NDF, respectively. The economic parameters: Revenue, Total Expenses, and Gross Margin showed quadratic behavior depending on the NDF content in the diet. The costs of concentrate and silage showed linear behavior, as did the costs of daily gain and the carcass equivalent cost (P<0.05). The maximum point of the revenue estimate (R$/animal) was 29.9% NDF, for the total expenditure on food (R$/animal) was 26.1% NDF, and 32.5% NDF for the gross margin (R$/animal). We recommended 25 to 32.5% NDF in diet to obtain maximum productive and economic performance when finishing Nellore young bulls in confinement. Keywords: confinement, economic viability, performance ...