It was evaluatednitrogen compounds and microbial protein synthesis in heifers fed diets containingcoffee hulls (0.0; 8.75; 17.25; and 26.25% of dry matter) replacing ground cornconcentrate at the following levels of coffee hulls in the total diet dry matter:0.0, 3.5, 7.0 or 10.5%. It was used 24 crossbreed heifers (7/8, 15/16 and 31/32Holstein-Zebu), which were distributed in a random block design made up accordinglyto the weight of the animals. Spot samples of urine were colleted aproximatellyfour hours after morning feeding and were used to estimate microbial proteinsynthesis by using urine purine derivatives. It was not observed effect of coffeehull levels in the diet on total nitrogen intake (160 g/day) and nitrogen excretionin the urine (87.4 g/day). The inclusion of coffee hull in the diet linearlyincreased nitrogen excretion in feces, as well as nitrogen balance. There waslinear reduction in urinary excretion of allantoin, in total purine derivativeand absorbed purine, which reduced 0.715, 0.873, and 0.954 mmol/day to eachcoffee hull unity added to the concentrate, respectively. Coffee hull alteredmicrobial protein synthesis, which reduced in 0.687 g/day to each coffee hullunity added to the concentrate. Reduction in microbial protein synthesis canreduce weight gain in heifers fed coffee hulls.
