Feed Processing. I. Ration Effects on Rumen Microbial Protein Synthesis and Amino Acid Composition

Five rumen-fistulated mature cattle, including two sets of identical twins, were fed succulent alfalfa pasture, alfalfa hay, or a mixed (1:1) alfalfa hay and sorghum grain ration. The last was fed both unprocessed and processed. Processed, the grain was expanded to achieve 100% gelatinization of starch and hay was finely ground. The amino acid makeup of rumen bacterial or protozoal protein was remarkably similar for all rations and for all animals. However, the amino acid compositions of protozoa and of bacteria were quite different. The processed feed lowered rumen ammonia concentration 50% and increased bacterial nitrogen concentration 50% when compared with unprocessed feed. Thns, while bacteria synthesized more protein on the more readily fermentable ration, quality of protein did not change.