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)

Abstract

Four cannulated sheep were used to study ruminal fermentation of a diet consisting of 60% sugar cane tops ( Saccharum officinarum), 30% corn stubble ( Zea mays), 10% King grass ( Pennisetum purpureum) and 0% (control), 10, 20 or 30% controlled-release urea supplement (CRUS) (diets 1, 2, 3 and 4, respectively). Average ruminal pH did not differ among diets ( P>0.05), but during the first 6 h of sampling tended to be higher for CRUS diets. Ammonia concentrations were higher ( P<0.01) in all treatments over controls, indicating microbial protein generation. Acetic acid production (mM/1) decreased ( P<0.05), propionic acid increased ( P<0.05), while butyric acid production 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 produced more of these energy sources. Supplementation of the high fiber diets with 10, 20 or 30% CRUS increasingly improved rumen fermentation, ammonia supply and VFA production. The results show that low quality forages (up to 70% DMI) can be used efficiently by sheep when conditions for ruminal microorganism are improved with a controlled-release urea supplement.