Effect of a controlled-release urea supplement on rumen fermentation in sheep fed a diet of sugar cane tops (Saccharum officinarum), corn stubble (Zea mays) and King grass (Pennisetum purpureum)

Four cannulated sheep were used to study ruminal fermentation of a diet con sisting of 60% sugar cane tops (Saccharum officinarum), 30% corn stubble (Z ea mays), 10% King grass (Pennisetum purpureum) and 0% (control), 10, 20 or 30% controlled-release urea supplement (CRUS) (diets 1, 2, 3 and 4, respec tively). Average ruminal pH did not differ among diets (P > 0.05), but duri ng the first 6 h of sampling tended to be higher for CRUS diets. Ammonia co ncentrations were higher (P < 0.01) in all treatments over controls, indica ting microbial protein generation. Acetic acid production (mM/1) decreased (P < 0.05), propionic acid increased (P < 0.05), while butyric acid product ion did not differ among CRUS diets and controls (P > 0.05). Total amounts of ruminal VFA were lowest (P < 0.01) in controls, while CRUS diets produce d more of these energy sources. Supplementation of the high fiber diets wit h 10, 20 or 30% CRUS increasingly improved rumen fermentation, ammonia supp ly and VFA production. The results show that low quality forages (up to 70% DMI) can be used efficiently by sheep when conditions for luminal microorg anism are improved with a controlled-release urea supplement. (C) 2001 Else vier Science B.V. All rights reserved.