Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Animal Science


Protein is often a limiting nutrient in animal diets. As ruminant animals have the ability to convert large quantities of nonprotein nitrogen to protein, the cost of protein supplementation can be greatly reduced by substituting cheaper nonprotein nitrogen compounds in protein supplements for certain amounts of preformed protein. This process is mediated through rumen microorganisms and, to date, urea has been the most widely used nonprotein nitrogen compound in ruminant diets. Efficiency of urea utilization may be affected by several factors. Among these are level and source of energy, level and source of protein and percent urea in the total diet and in the supplement. Other essential nutrients in the diet should also be properly balanced. There has been a tendency in recent years to use higher levels of urea than was earlier recommended. Under some conditions, urea has been satisfactory as the only source of supplemental protein to diets for cattle. However, consideration must be given to likely problems of palatability and potential toxicity as well as efficiency of urea utilization. Although lower feed costs have resulted from substituting cheaper nonprotein nitrogen sources for preformed protein, animal performance has often been at a lower rate. This has-prompted investigations towards improvement in utilization of urea nitrogen by use of various supplements with urea. There has been a considerable amount of interest in possible effects from amino acid supplementation since protein needed by animals is a need for amino acids. Some experiments have shown that the sulfur-containing amino acids are the first limiting ones when ruminants are fed diets with urea furnishing practically the only source of nitrogen. It has also been shown that rumen microorganisms are able to synthesize the sulfur-containing amino acids when ample sulfur is present. More information is needed as to the possible benefits of amino acids, particularly the sulfur-containing ones, and sulfur supplementation when urea is used as the only supplemental protein under various conditions of protein and energy levels in the basic diets. The objective of this research was to study effects of sulfur and methionine hydroxy analogue additions to high-urea supplements fed to growing-finishing beef cattle. A feeding trial was conducted in which weight gains, feed consumption and feed efficiency were used as measures of performance.

Library of Congress Subject Headings

Cattle -- Feeding and feeds
Urea as feed
Feed additives



Number of Pages



South Dakota State University