Abstract The present experiment aimed to evaluate the partial replacement of corn with chocolate byproducts or protected fats in diet lactating cows on feed utilization, blood profile and lactation performance. Fifty multiparous Holstein (560±22 kg BW, 3±1 parity, 7±1 days milk, previous milk production 34±3 kg/d), were randomly assigned 5 treatments a completely randomized design for 90 days. ...