This study was aimed to examine the nutritional efficiency of the balanced supply of flavonoids from the crude or ethanol extract of brown propolis on behaviour, productive performance and carcass traits of lambs in feedlot. Twenty four male lambs were divided into 4 groups (6 animals in each) and fed diet supplemented with: crude brown propolis [13 g/kg dry matter (DM)], propolis ethanol extract (15 ml/kg DM), sodic monensin (0.032 g/kg DM) – positive control, or diet without any enrichment (negative control). The basic diet was a total mixed ration with roughage:concentrate ratio of 500:500 (w/w). In animals receiving crude propolis (P < 0.05) DM intake was higher than in animals fed sodic monensin in the diet. The use of feed additives did not affect feeding behaviour and lambs performance. Carcass yield was lower (P < 0.05) in lambs receiving diet with sodic monensin than in lambs fed diets with crude propolis. Also the propolis extract addition into diet decreased carcass yield in comparison to control group. Propolis addition altered the fatty acid profile of meat reducing saturated fatty acid content and increasing unsaturated one in comparison to control group. So, brown propolis supplementation can influence lamb carcass traits and meat quality; however the form of propolis is an important factor. The possible addition of propolis into animal feed can be important from human nutrition point of view.