Fourty Aberdeen Angus steers were used to evaluate the effects of monensin, soybean oil and nitrogen source (soybean meal or urea) on feedlot performance of steers fed 90% concentrate diets. The monensin decreased dry matter intake of soybean meal supplemented diets and decreased the body weight at 56 and 112 days. The soybean oil decreased the average daily gain from days 57 to 112 and 1 to 112. While, monensin showed a decreased on the average daily gain in these periods in the diets containing soybean meal as nitrogen source. The soybean oil decreased feed efficiency on all periods and soybean meal, as compared to urea diets, in the days from 57 to 112 and 1 to 112 periods. The monensin increased feed efficiency in 7.4% for the diets containing soybean meal, without soybean oil, but it did not change the feed efficiency for diets containing urea. In contrast, monensin decreased feed efficiency in 13% for the diets containing soybean meal and soybean oil.
feedlot; feed efficiency; monensin; oil; protein; steers
