Date of Award:


Document Type:


Degree Name:

Master of Science (MS)




William F. Sigler


The urolithiasis condition investigated occurred at a "hard water" hatchery in Utah after the trout were changed from a meat diet to a commercial pelleted fish feed as a sole sustaining diet in 1961. Numerous diet modifications proved unsuccessful in preventing urolithiasis at the hatchery. It was eventually determined that different commercial diets resulted in varied percentages of trout developing urolithiasis. The urolithic deposits found in the kidney tubules were amorphous and composed of calcium phosphate (apatite) and an organic matrix. Bacterial contamination of the kidneys was not an important factor in the formation of urolithiasis. Rainbow trout containing urolithic deposits showed gradual deposit regression when transferred into a "softer" water supply.

Pelleted experimental diets containing sodium bicarbonate and/or sodium fluoride were fed to two strains of rainbow trout reared in a "softer" water supply normally causing no urolithiasis problems. The diets with the sodium bicarbonate added resulted in a significant occurrence of urolithiasis when fed to trout for 30 days. The addition of sodium fluoride to the diet was not significant in producing urolithiasis in trout. One experimental diet (low sodium bicarbonate-sodium fluoride) and one strain of fish (Soap Lake) appeared to influence the number of trout developing urolithiasis although the increase was not significant. All levels of statistical significance were tested at the 5 percent level.



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