Masters Theses

Alan Thompson

Date of Award

8-1957

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Husbandry

Major Professor

M. C. Bell

Abstract

In recent years an increasing amount of attention has been given to the mineral fraction of feeds and to its importance in animal nutrition. As a result, it is now well-recognised that the value of a dietary source of an element depends not only upon its total content, but also upon the ability of the animal to extract that element and to retain it for use in metabolic processes. A considerable body of evidence now exists to show that the availability of the inorganic elements, to the animal, may differ widely in various livestock feeds and supplements. Insufficient data are available, however, to allow any great im-provement in the present system of recommending dietary allowances for min-erals, which is based upon the total content of the element with no allow-ance being made for the non-available fraction. In addition, it is be-coming apparent that the percentage availability or digestibility of an element is not a constant for a particular feed but varies with the species of animal, its age and past nutritional history and other factors. The introduction of suitable radioisotope procedures has made pos-sible a deeper understanding of the various metabolic processes associated with the ingestion and subsequent utilization and distribution of the in-organic elements. In addition, such methods have greatly helped in obtain-ing a more accurate estimate of the true digestibilIty of mineral elements in feeds under varying dietary and environmental conditions. Considerable data are now available from this type of study, particularly for the ele-ments calcium and phosphorus. Several reports exist which strongly suggest that interactions be-tween both the organic and inorganic constituents in the alimentary tract of an animal may increase or decrease calcium and phosphorus absorption. lt would therefore seem pertinent to study some of these possible effects upon availability and to estimate their magnitude. Little information is available regarding the effects of aluminium and zinc upon the availability of calcium and phosphorus in ruminants, though some does exist for laboratory animals. The element aluminium is of considerable interest in view of its suggested use as an alleviator in fluorine toxicity while the increasing nutritional roles of zinc, and the suggestion of a relationship to calcium in parakeratosis, make it an ele-ment worthy of study. The present investigation was conducted to determine the effects of dietary aluminium and zinc upon the absorption and retention of calcium and phosphorus in lambs. Conventional chemical and radiochemical balance ex-periments were made which allowed the calculation of data, for the net ab-sorption, endogenous fecal excretion and true digestibility of calcium and phosphorus.

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