Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Animal Science

First Advisor

Robbi H. Pritchard


The ruminant's ability to convert low quality and non-protein nitrogen (NPN) to high quality protein is as important as their ability to utilize cellulosic feeds. This unique characteristic will continue to be exploited in the future with increasing emphasis being placed on noncompetitive feedstuffs. There has been considerable progress in developing alternative energy sources in beef cattle diets. There has not been the same success in replacing dietary high quality preformed proteins with urea or other NPN sources in most production situations. The complexity of the digestive system in ruminants is well recognized by all who work with diet formulation for these species. Digestion by ruminants is a two step process, first by microbes in the reticulorumen, and secondly, true gastric digestion by the host animal. This results in our need to consider two separate but interdependent ecosystems when formulating diets for ruminants. Since the introduction of NPN as a source of nitrogen for microbial protein synthesis many questions have arisen concerning animal protein requirements. NPN utilization requires readily fermentable carbohydrates, limiting the production situations in which NPN can replace high quality protein. Young rapidly growing cattle or cattle on low quality feeds continue to require supplemental high quality protein like soybean meal to maximize performance. Conceivably, additional protein is required to meet needs for production and possibly to overcome amino acid imbalances. The need to develop a technique allowing us to directly measure the net protein and amino acid requirements of beef cattle and how ruminal fermentation will modify dietary nitrogen components is apparent. The development of an in vivo model will provide the tool needed to measure the true value of typical protein supplements and screen possible alternative nitrogen sources. To establish such a model, one must first resolve certain aspects of methodology. The objectives of this project were to develop a protein-free diet that is consumed at production intake levels, to validate the use of indigestible acid detergent fiber as an internal phase indicator in this diet and to investigate the potential of urinary allantoin as a means of estimating ruminal microbial protein synthesis.

Library of Congress Subject Headings

Beef cattle -- Feed utilization efficiency

South Dakota State University Theses



Number of Pages



South Dakota State University