Feed Processing. VII. Effect of an Expansion-processed Mixture of Grain and Urea (Starea) on Rumen Metabolism in Cattle and on Urea Toxicity

Starea was compared with several other feed processing treatments for utilization of urea.It is an expansion-processed mixture of gelatinized grain starch and urea.All rations contained about 5% urea, and the grain was sorghum.In a first experiment 2 pairs of identical twin cattle were fed rations of urea and grain that had been a) cracked, b) finely ground and pelleted, c) expanded or d) made into Starea.The rations were changed each week, consequently after 4 weeks the individual animal had been fed all 4 rations.The sequence was repeated once.Finely ground pelleted grain, expanded grain and Starea were not different from one another in their effect on rumen ammonia concentration.However, all 3 rations compared with cracked grain lowered rumen ammonia concentration (P < .01).Starea was eaten more readily than the 3 other rations.In a second experiment, Starea and the cracked grain plus urea ration (control) were fed to the 2 pairs of identical twin cattle.The total quantity and concentration of bacterial and protozoal nitrogen were significantly greater in the rumen contents of the Starea-fed animals than in those of the controls.The rumen ammonia concentration of the Starea-fed animals was lower than that of the controis.These differences approached statistical significance (P < .05) in the 1and 2-hr samples.