The addition of 0; 5; 10 and 15% cassava bagasse, based on the dry matter of the total diet of crossbred Holstein v. Zebu cows, was evaluated on milk production and composition and on the impacts of diet costs. The animals, weighing an average of 478.5 kg, were in the middle third lactation period. Diet with 15% cassava bagasse provided a 13.2% increase in production when compared to control. Feed conversion had a quadratic effect with minimum point at 4.2% of cassava bagasse inclusion. Crude protein, the only milk component that changed, increased linearly with the inclusion of cassava bagasse levels. Treatment with 15% cassava bagasse caused a more effective operational cost (42.8% higher when compared to control) and the highest leveling point for milk production and price. The lowest leveling points were treatments with 5 and 10% inclusion of cassava bagasse, which had the best economic results. Concentrates caused cost increase, particularly when roughage : concentrate ratio decreased due to higher cassava bagasse inclusion levels.