Feedlot-finishing lambs with different levels of soybean pre-cleaning by-product as the roughage source

An experiment was conducted in the Sheep Farming Laboratory at the Federal University of Santa Maria to examine the effect of different levels of replacement of sorghum silage with soybean pre-cleaning by-product (SPCB) on nutrient intake, performance and feeding behavior; as well as to undertake an economic analysis of feeding finishing lambs in a feedlot system. The study involved 32 uncastrated Texel × Ile de France crossbred male lambs weaned at 60 days of age. Treatments consisted of diets in which the roughage source (sorghum silage) was replaced with SPCB at the levels of 0, 33.5, 66.5 or 100% (DM basis). A 45:55 roughage:concentrate ratio was used (DM basis). The diets were composed of a roughage feed based on sorghum silage and/or SPCB, and a concentrate consisting of crushed maize, soybean meal and limestone. In addition, mineral salt was freely available to the animals. The lambs were slaughtered upon reaching the pre-established live weight of 35 kg. Intake on a DM basis showed a quadratic response (P ≤ 0.05) in all forms it was evaluated and expressed, except for the NDF fraction, which increased linearly (P ≤ 0.05) with SPCB inclusion. Average daily weight gain was not significantly influenced (P > 0.05) by the different SPCB levels, averaging 292 g/day. As regards the feeding behavior characteristics evaluated, the number of daily feeding bouts increased linearly (P ≤ 0.01) with the SPCB content of the diets. Total feed cost decreased linearly (P ≤ 0.01), whereas the profit per kilogram of gain and profit obtained per day in the feedlot period increased linearly (P ≤ 0.01) with SPCB inclusion. The use of soybean pre-cleaning by-product as the roughage source in the finishing of feedlot lambs proved to be a viable alternative in both the productive and economic terms.