The effect of four levels (0; 33; 66 and 100%) of substitution of sorghum grain (Sorghum bicolor L. Moench) by oats grain (Avena strigosa) in the concentrate of diets for feedlot finishing steers, was studied. Steers (19 months old and initial weight of 381 kg) were fed a diet containing 60% roughage and 40% concentrate, formulated for ADG of 1.2 kg/animal. During the adaptation period of seven days and in the first half of the experimental period (35 days) the roughage used was sorghum silage (Sorghum bicolor L. Moench) For the second half of the experimental period (32 days), the roughage used was corn silage (Zea mays). During the adaptation period, the diets with higher levels of oats promoted better animal performance, however, during the experimental period, the increase of oats proportion in the concentrate in substitution to sorghum grain resulted in a linear decrease of live weight gain (1.292; 1.251; 1.217 and 1.051 kg, respectively, for 0; 33; 66 and 100% of oats), as well as linear increase in the amount of feed consumed per kg of live weight gain (7.911; 8.000; 8.220 and 9.212, respectively). The decrease in live weight gain as the level of oats increased, was associated with the higher concentration of NDF (29.3 vs 16.1%) and lower concentration of digestible energy (3.179 vs 3.590 Mcal/kg) of oats compared to sorghum, which limited the dry matter intake and digestible energy intake/animal/day. The use of a roughage with better quality during the last half of the finishing period, provided uniformity of weight gain during the whole feedlot period, as a result of higher dry matter intake and digestible energy intake.
digestible energy; feedlot; NDF; oat grain; sorghum grain; weight gain
