Several strategies have been used to improve fat deposition and fatty acids composition; however, most of them are focused on reducing saturated fatty acids by increasing the content polyunsaturated acids. This study aimed to evaluate performance, carcass traits and fatty acids composition in the intramuscular fat of steers. Forty crossbred yearling steers (260 ± 5.9 kg LW) were supplemented with four levels of a glucogenic substrate: 0, 20, 40 and 60 g/d (T1, T2, T3 and T4, respectively). Animals were slaughtered after feeding trial, carcass traits and intramuscular fat samples were obtained. Final weight (FW) and average daily gain (ADG) increased with supplementation (p< 0.05); however, dry matter intake decreased in T2 (p< 0.05). Hot carcass weight, area rib eye and rib fat thickness increased with supplementation (p< 0.05). Likewise, saturated, monounsaturated and polyunsaturated fatty acids contents increased with supplementation of 60 g of glucogenic substrate (T3) versus T1 (p< 0.05). Additionally, Ω6/Ω3 ratio was different between treatments (p< .05). This ratio increased 20% with the addition of 20 g of glucogenic substrate compared to T1. Supplementation with 40 g/d of glucogenic substrate may improve fat deposition and fatty acids composition in intramuscular fat as well as enhance performance and carcass traits of feedlot cattle.