Souza et al., 2006. Rev. Bras. Zootec., 35 (4 Supplement): 1860-1865

The effect of replacing ground corn with coffee hulls on N balance and microbial protein synthesis of lactating dairy cows was evaluated in this trial. 12 crossbred Holstein-Zebu cows yielding on average 23.4 kg/day of milk were used in the study. Microbial protein synthesis was estimated by excretion of purine derivatives in urine and milk. The animals were fed diets containing the following coffee hulls levels (% DM): 0.0, 3.5, 7.0 or 10.5%. Spot urine samples were collected ~4 h post-feeding. Regression analysis showed no effects of dietary coffee hulls levels on total nitrogen intake (441.3 g/day) and excretion of urine N (190.8 g/day) and milk N (114.7 g/day). However, feeding coffee hulls to lactating dairy cows increased faecal N excretion resulting in negative N balance. The increased dietary levels of coffee hulls did not affect excretions of milk allantoin (294.6 mmol/day), urinary allantoin (21.3 mmol/day), uric acid (42.3 mmol/day), and purine derivatives (358.2 mmol/day). Microbial protein synthesis estimated by urinary excretion of purine derivatives averaged 266.3 g/day and did not differ among the diets. In addition, efficiency of microbial protein synthesis averaged 136.8 g of microbial N per kg/TDN and also did not differ among diets.