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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

Royce J.Emerick


Experiments with sheep were conducted to study dietary factors that either promote or minimize silica urolith formation. Additional experiments with a rat model were conducted to investigate dietary zinc, silicon, and copper effects and interrelationships influencing silica urolithiasis. The incidence of silica urolithiasis in sheep fed high-silica diets containing a calcium to phosphorus ratio of 2:1 was higher when supplemented with 1 % dietary NaHCO3 (an alkali-forming salt) than when supplemented with 1 % NH4CI (an acid-forming salt). A second sheep experiment investigated the prophylactic value of NH4CI additions to a high silica diet when the Ca:P ratio in the diet was either high (2:1) or low (1 :1). Regardless of the Ca:P ratio in the diet, the NH4CI supplemented sheep had a 0 incidence of silica uroliths. Non-supplemented sheep fed diets having Ca: P ratios of 2: 1 or 1 : 1 had silica urolith incidences of 13% and 18%, respectively. A rat experiment was conducted to determine if a previously observed dietary ZnSi antagonism was prevalent enough to reduce urinary silica concentrations and silica urolithiasis in rats fed a high-Si diet. Some physiological antagonisms were present. however, only a trend toward reducing urolith formation with increasing concentrations of dietary Zn was evident. Urinary volume, pH, and urinary concentrations of P, and Ca were similar among all Zn-treatment groups. A second rat experiment examined potential interactions between two concentrations of dietary Cu and three of Zn in animals fed high levels of dietary silica. Where Cu was deficient, the Zn-excess group had the highest (over Zn-deficient or Znadequate groups) incidence of siliceous uroliths. Where Cu was adequate, the Zndeficient group had the highest incidence of siliceous uroliths. Cu and Zn had little or no effect on urinary volume and pH, or concentrations of P, Ca, and Si. In the sheep studies, dietary factors promoting increased urinary volume, low urinary pH, and low urinary Ca:P ratios provided the best protection against siliceous urolith formation. The data from rat studies indicate that a Zn-Si antagonism is not of sufficient magnitude to be of use in the prevention of silica urolithiasis. However, the data suggest that Zn deficiency and, to a lesser extent, Cu deficiency may contribute to silica urolith formation in rats fed high-Si diets.

Library of Congress Subject Headings

Sheep -- Diseases -- Prevention Silica Urinary organs -- Calculi -- Prevention



Number of Pages



South Dakota State University


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