Uromol as a source of dietary nitrogen for ruminants: metabolic and rumen fermentation studies on buffalo calves

SUMMARY The nutritive value of uromol, a heated product of urea and molasses, was compared with raw urea–molasses and groundnut meal in three metabolic trials on buffalo calves. The non-protein nitrogen (NPN) as urea or uromol contributed about 65, 48 and 30% of the nitrogen in the experimental concentrate mixtures, replacing partially or completely the groundnut meal of the control diets. The results showed that at 65% nitrogen replacement, the crude fibre and cellulose digestibilities and the nitrogen retention of the uromol diet was similar to that of the control but was significantly (P < 0·05) higher than the urea–molasses diet. At 48% nitrogen replacement the nitrogen retention in the uromol-fed animals was still significantly (P < 0·05) higher than the urea–molasses fed group. At 30% nitrogen replacement, the differences between the control, urea–molasses and uromol groups were not significant. In vivo rumen studies with the diets containing 50% NPN replacement showed lower but sustained ammonia-N with uromol than the urea–molasses diet. The total volatile fatty acids (TVFA) in rumen fluid, though initially higher in the control and uromol groups, were not significantly different from the urea–molasses group. Abomasal studies with diets containing 65% N as urea or uromol indicated a higher total nitrogen content in the abomasal fluid of the control and uromol-fed animals than the urea-fed animals. The 24 h abomasal passage of total-N/100 g nitrogen consumed was 95·5, 93·5 and 77·9 g in control, uromol and urea groups, respectively. The TCA-precipitatable-N (TCA-N) was also higher in the first two groups. These studies suggest that uromol is safer and has a better feeding value than urea–molasses at high rates of nitrogen replacement.