The economic viability of the inclusion of urea in the ration for feedlot lambs

SUMMARY The aim of this study was to evaluate the economic viability of the inclusion of urea in the ration provided to feedlot lambs. Twenty-four non-castrated male lambs, crossbred Dorper, with 2-5 months of age and a body weight (BW) of 25.0 ± 4.3 kg were used. A completely randomized design with four treatments and six replicates was adopted, in which the treatments were urea levels of 0.0, 0.5, 1.0 and 1.5% in the ration, on a dry matter (DM) basis. Lambs were fed ad libitum for 56 days and slaughtered at a BW of37.9 ± 5.1 kg. The analyzed economic indexes were the cost of the rations, cost of marginal factor (CMF), revenue of marginal factor (RMF), net revenue (NR) and benefit: cost ratio (BCR). The ration without urea presented the highest cost (0.30 US$/kg DM) and the ration with 1.0% DM of urea had the lowest cost (0.23 US$/kg DM). The CMF had a quadratic response to the urea level, reaching the lowest value (0.28 US$/day) with the addition of 0.9 to 1.0% DM of urea. The lowest and the highest NR values were obtained from the rations without and with 1.5% DM of urea, respectively (0.26 and 0.34 US$/day). The ration without urea had a worse BCR (1.74), whereas the ration with 1.0% DM of urea resulted in a better BCR (2.09). A better economic return for lambs finishing in feedlots is obtained with rations containing 1.0 to 1.5% DM of urea.

摘要 本研究旨在评估在育肥羔羊日粮中添加尿素的经济可行性。试验选取24只2~5月龄、初始体重为25.0±4.3 kg的杜泊杂交未去势公羔羊。采用完全随机试验设计，设置4个处理组，每组6个重复，各处理组日粮以干物质（dry matter, DM）为基础的尿素添加水平分别为0.0%、0.5%、1.0%和1.5%。试验期内羔羊自由采食，饲养周期共计56天，最终屠宰时平均体重为37.9±5.1 kg。本研究分析的经济指标包括日粮成本、边际要素成本（cost of marginal factor, CMF）、边际要素收益（revenue of marginal factor, RMF）、净收益（net revenue, NR）及效益成本比（benefit: cost ratio, BCR）。不含尿素的日粮成本最高（0.30美元/千克干物质），日粮干物质基础尿素添加量为1.0%的组成本最低（0.23美元/千克干物质）。边际要素成本随尿素添加水平呈二次响应趋势，当日粮干物质基础尿素添加量为0.9%~1.0%时，边际要素成本达到最低值（0.28美元/天）。净收益的最低值与最高值分别来自未添加尿素的日粮组（0.26美元/天）和添加1.5%干物质尿素的日粮组（0.34美元/天）。未添加尿素的日粮组效益成本比最差（1.74），而日粮干物质基础尿素添加量为1.0%的组效益成本比最优（2.09）。综上，育肥羔羊日粮中添加1.0%~1.5%的干物质基础尿素可获得更优的经济效益。