The economic evaluation of the use of four substitution levels (0; 33; 66 e 100%) of sorghum grain (Sorghum bicolor L. Moench) by oat grain (Avena strigosa) in the concentrate of diet of steers during feedlot finishing, was studied. The animals, 19 months old and with initial average weight of 381kg, were fed a diet with 60% of roughage and 40% of concentrate, containing crude protein for a weight gain of 1.2kg/animal/day. During the adaptation period and the first half of the experimental period (35 days) the roughage used was sorghum silage, during the second half of the experimental period (32 days) the roughage used was corn silage (Zea mays). When sorghum silage was used the costs of the diet per animal per day were R$ 1.062; 0.970; 0.865 and 0.725, respectively, for the substitution levels 0; 33; 66 and 100%. The diet costs to produce 1kg of weight gain were R$ 0.82; 0.74; 0.78 and 0.65, respectively. When corn silage was used, the cost of the diets increased as a result of the increase in dry matter intake and the higher production cost of corn silage, however, the daily weight gain was maintained close to 1.2kg animal-1 as preconized. The costs per animal per day of diets containing corn silage were R$ 1.401; 1.208; 1.063 and 0.906 and R$ 1.083; 1.011; 0.799 and 0.916 for the production of 1kg of weight gain, respectively, for the substitution levels 0; 33; 66 and 100%. Total costs of the different diets per animal during the whole period of 67 days were R$ 82.517; 72.959; 64.587 and 54.645, resulting a gross income per animal of R$ 95.22; 92.20; 89.66 and 77.46, originating a positive difference of R$ 12.70; 19.24; 25.07 and 22.81 per animal, respectively, for substitution levels 0; 33; 66 and 100%.
costs in feedlot; cost of weight gain; alternative diets; economics in beef cattle; income
