Nitrogen fertilization can be used to increase production for area, as well as to improve the grains nutritional value. The aim of this study was to evaluate the chemical composition of two linseed cultivars (Brown and Golden) submitted to increasing doses of nitrogen fertilization in a completely randomized design. The Brown and Golden flax sowing was in April 2014, using 40 kg of viable seeds ha-1 and 100 kg ha-1 of diammonium phosphate (16-46-00) as fertilizer. It was evaluated the increasing doses of N fertilization in the cover: 0, 50, 100, 150 and 200 kg of N ha-1, applied in the urea form. For the fatty acids (FA) analysis, a composite sample of each variety was performed for the treatment 0 and 200 kg N ha-1. The composite samples were grounded in a multi-use mill with cooling jacket. The cooling was aimed to avoid the heating of the samples during their processing, in order to reduce the chances of FA profile alterations. The application of nitrogen positively influenced the production of grains and oil ha-1 of the cultivars, improved the Brown flax dry matter in vitro digestibility and the Golden flax neutral detergent fiber, ether extract and crude protein amounts. The cultivar Brown flax presented higher production of grains and oil ha-1 when compared to Golden flax, which presented lower neutral detergent fiber, crude protein, total carbohydrates and higher amounts of ether extract. The Golden flax was nutritionally healthier, as it presented higher proportions of C18:3 n3, unsaturated fatty acids, unsaturated/saturated fatty acids and hypocholesterolemic index. Both cultivars have potential ingredients to be used in animal feed, aiming to improve the quality of the final product.