The effects of inclusion of by-products (cocoa, cassava peel, cassava stalk, and corn gluten meal) and their levels (10 and 30%), replacing part of corn silage on intake, digestibility of nutrients, microbial protein production, nitrogen balance, prediction of digestible fractions, and total digestible nutrients were evaluated. The intakes of dry matter and neutral detergent fiber were affected by source of by-product, which affected the digestibility of ether extract and non-fibrous carbohydrates. The energy corn gluten meal was 17% higher than that of corn silage, while the values for cassava peel, cocoa, and cassava stalk were 10, 19, and 38% lower than the value for corn silage. The source and the level of by-product did not affect the urinary excretion of total purine, purine absorbed, microbial nitrogen, and microbial efficiency. The source of by-product affected intake, nitrogen compounds, excretion in feces and urine, and nitrogen balance. The corn gluten meal and cassava peel are by-products with potential to partly replace the energhetic concentrates, with no influence on the intake, digestibility, microbial efficiency, and nitrogen retention
alternative feed; agro-industrial waste; nutritional value
