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In Vitro Observations upon the Nature of Protein Influences upon Urea Utilization by Rumen Microorganisms^{1, 2,}

Ohio Agricultural Experiment Station

Abstract

Three series of experiments were used in studying the nature of protein influences upon urea utilization by rumen microorganisms making use of the artificial rumen technique. Urea utilization in the first series was studied in the absence of conventional protein compared with urea utilization in the presence of respective proteins, casein and gelatin, having widely different amino acid compositions. In the second series, further comparisons were made with urea in the presence of varying respective levels of casein and gelatin, making use of two different mathematical formulas in computing urea utilization. The third series of experiments compared urea utilization as influenced by the presence of 6 purified proteins and 6 protein-rich feeds commonly fed to livestock.

The results are interpreted upon the basis that the nitrogenous requirements of rumen microorganisms are relatively simple in nature, essentially involving only ammonia and not involving the more complex forms of nitrogen, such as amino acids. In arriving at this conclusion concerning nitrogenous requirements, other requirements such as the energy and mineral needs of rumen microorganisms are also discussed in relation to protein influences upon urea utilization.

¹ Supported in part by grants from E. I. du Pont de Nemours and Company, Wilmington, Delaware, and Swift and Company, Chicago, Illinois.

² Published with the approval of the Director of the Ohio Agricultural Experiment Station.