THE EFFECT OF NIACIN AND MONENSIN ON THE PERFORMANCE OF YOUNG BULLS AT FEEDLOT

The objective of this study was to evaluate the effects of supplementa tion of combined and single monensin and niacin on the productive perf ormance of crossbred young bulls (european/zebu) aged 11 months and in itial average liveweight of 248 kg. The experimental design was a fact orial randomized arrangement. The treatments were: T1-check, T2-niacin , T3-monensin and T4-niacin+monensin. All the treatments were isoprote ic (11 %CP) and isoenergetic (78% TDN), composed of 57.3% roughage and 42.7% concentrate (soybean meal, maize, minerals and buffer). Data wa s collected over a period of 85 days, with liveweight measured every 2 8 days. It was conclued that, for this diet, the single supplementatio n of niacin does not increase the performance of bulls, and therefor i t is not recommended. However, the ionophore monensin, single or on in combination with niacin, improves the performance of the animals up t o 56 days of feedlot.