Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

O. Glen Hall

Committee Members

M. C. Bell, Charles S. Hobbs, H. J. Smith


[From the Introduction]

Phosphorus deficiency has limited livestock production since the beginning of recorded history. This is understandable in view of the essentiality of phosphorus to various life processes and of the problems of providing adequate amounts of available phosphorus in rations for livestock.

One of the best known functions of phosphorus is its importance in building bones and teeth. Also, it has an equally important function in every living cell of the body. It is essential for the utilization and metabolism of the other nutrients such as proteins, fats, and carbohydrates. Muscles cannot grow and divide, and cells cannot move except under the influence of phosphorous. This element is, therefore, very closely associated with the basic nature of living matter.

In the early days of nutrition research investigators worked long and hard in proving that animals could utilize the inorganic form of many elements, such as phosphorous, as well as their organically bound forms. Later it was rather widely assumed that all inorganic chemical forms of an element such as phosphorous were of equal feeding value. More recent studies have shown that this is not the case, and that a given weight of an element from one source may be less effective than the same amount from another source.

Increased demands for feed phosphorus and shortages of bone meal have been greatly increased the need for other sources of phosphorus, and several different sources are now available.

Among the most common of these sources are defluorinated domestic rock phosphates, dicalcium phosphate, Curacao Island phosphate, and a limited amount of bone meal and phosphoric acid.

The biological availability of phosphorus in these supplements to ruminants has not been widely studied. This is due to the expense and length of time required for conventional metabolism studies. During the past few years an in vitro technique, involving washed rumen microorganisms, has been proposed as quick and less expensive method of assaying phosphorus supplements. The validity with which results from this technique can be applied directly to the animal has not been determined.

With the advent of the radioisotope dilution technique, the true digestibility of the phosphorus in a supplement can now be determined. The specific objective of the experiments reported in this thesis was to determine the true digestibility of the phosphorus in two defluorinated phosphate supplements using the isotope dilution technique. The apparent availability of the phosphorus in both supplements was determined with washed rumen microorganisms prior to the initiation of the radioisotope study. Thus it was possible to compare the results from both techniques.

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