Abstract This study aimed to measure the carbohydrate and protein fractioning of silage of Brachiaria brizantha cv. Marandu (BBS). The experiment was a completely randomized design with five treatments and five repetitions to evaluate the inclusion of dehydrated brewery residue (DBR) to Marandu grass silage at levels of 0, 10, 20, 30 and 40% fresh matter basis. The DBR inclusion resulted in a linear reduction (P<0.05) of total carbohydrate content, which decreased 0.35% per unit of residue added. The content of fraction B2 decreased linearly as DBR was added (P<0.05). Nitrogen content increased linearly when residue was added to silage of Marandu grass (P<005). Fraction A, obtained from Marandu grass, presented a linear increasing behavior according to the inclusion of DBR. This inclusion promoted a linear decrease (P<0.05) of fraction B1+B2, which resulted in a 0.37% reduction for each 1% of byproduct added. Dehydrated brewery residue is a good source of additives for ensiling Marandu grass, by considerably improving fractions of proteins and carbohydrates. The level of addition of 40% is recommended for providing better nutritional value to silage.