The objective of this experiment was to evaluate the effect of replacement of soybean meal by urea or starea on nutrient digestibility and ruminal parameters in bulls. Six Nellore bulls, with 420 kg of initial body mass, were used to evaluate the effects of replacing a true protein source (soybean meal), in a ruminal degradability protein deficient diet, by urea or starea, both in a ruminal degradability protein adjusted diets, on nutrient digestibility and ruminal parameters in beef cattle. In natura sugarcane bagasse was the only source of forage (20% of dry matter). Soybean meal treatment reduced (P<0.05) dry matter intake compared with urea and starea treatments. There was no difference between urea and starea treatments. There were no differences (P>0.05) in dry matter, organic matter, non-fiber carbohydrates, ether extract and crude protein apparent digestibility (%) among treatments. Acid detergent fiber and neutral detergent fiber digestibilities (%) were higher (P<0.05) for urea and starea treatments. There was no treatment effect and interaction treatment x time (P>0.05) for pH values, total rumen volatile fatty acid molar concentration and acetate, propionate, butyrate and acetate:proprionate ratio. The molar concentration of valerate, isobutyrate, isovalerate and branched-chain fatty acid were higher (P<0.05) for soybean meal treatment. There were no differences (P>0.05) between urea and starea. Total replacement of soybean meal by urea or starea, adjusting ruminal degradability protein for beef cattle is practicable.
beef cattle; rumen; protein; fibres; animal feeding
