“…Goularte et al (2010) found average concentrations of N-NH 3 of 37.40, 39.62, 35.59 and 34.13 mg/100 mL of rumen fluid for concentrate levels of 30, 40, 50 and 60%, respectively. It is noteworthy that high levels of N-NH 3 can mean bigger losses of nitrogen in the system, since, in order for there to be synthesis microbial protein and, consequently, use of N-NH 3 , there should be availability of carbon skeletons in synchrony with degradation protein in the rumen, which does not occur in diets with reduced starch and non-structural carbohydrates and/or sources of energy from fat, which should lead to loss of energy in the form of ATP, for processing into urea by the liver to urinary excretion, which probably did not occur in the present experiment, due to the lower concentrations of N-NH 3 .…”