Influence of Dietary Nitrogen on Nitrogen Metabolism in the Rumen

Abstract

In vivo trials, utilizing four fistulated steers in a Latin-square design, were conducted with four rations: casein + basal, urea + basal, soybean meal + basal, and cottonseed hulls (basal). Nitrogenous constituents, volatile fatty acids (VFA), and pH values were determined on rumen liquor taken at various intervals after feeding. Levels of urea nitrogen were determined on the jugular blood. The concentration of ammonia present in the rumen over a 12-hr period from the urea or casein ration was significantly higher (P < 0.01) than that observed when the basal ration was fed. The concentration of ammonia from the urea ration was significantly higher (P < 0.01) than that observed when the soybean meal ration was fed. Feeding of urea resulted in a significantly higher (P < 0.05) concentration of ammonia than did casein. Total VFA were influenced by nitrogen substrate. The casein ration was associated with greater quantities of propionic, butyric, and valeric acids than that observed when the other rations were fed, whereas the urea ration was associated with the highest quantity of acetic acid. © 1964, American Dairy Science Association. All rights reserved.