Ruminal Degradation of Monomethylol-Urea, Isobutylidene-Diurea, Urea and Soyabean-Meal and the Passage of Nutrients Through the Duodenum with Maize as Energy Source¹

Rumen and duodenum cannulated wethers were used to quantitate the extent of degradation of m onomethyloi-urea (MMU), isobutylidene-diurea (IBDU), urea and soyabean-meal (SBM) in a ground-maize based ration and to study the nitrogen components reaching the duodenum. The supplemented-NPN amounted to 44% of the total-N. Feeding was done twice daily at a 12 hr interval. The mean daily intake was 23 g N and 890 g OM. Mean estimates of the first three hours of feeding showed that 109, 108, 86 and 75 m moles of TVFA were produced on urea, IBDU, SBM and MMU supplemented diets; and correspondingly 49, 50, 62 and 43% of the ingested OM was lost preabomasum, respectively. A : P ratio was the highest with SBM (4.13), followed by urea (2.58), IBDU (2 33) and MMU (2.12). Half of the supplemented-N of IBDU was recovered as ammonia at the duodenum and was considered responsible for reduced feed intake. The daily non-ammonia-non-urea-N fraction at the duodenum was the highest for MMU (20 g), followed by urea (18 0 g), IBDU (16 9 g) and SBM (12 8 g). Maize proved as a ‘medium-release’ energy source and did not meet the energy needs of the quick ammonia-release urea, but proved beneficial for MMU. However. MMU supplementation favoured propionate fermentation, resulting in eneigy and nitrogen economy.