High dietary calcium to phosphorus ratio and alkali-forming potential as factors promoting silica urolithiasis in sheep.
Sheep were used to study factors previously found to promote silica urolithiasis in a rat model. In addition to high silica, these dietary factors included elevated calcium, a high calcium to phosphorus ratio and alkali-forming effects. Wether lambs had ad libitum access to a diet of 50% of grass hay and 50% ground oats plus supplement. Diet analysis was 3.4% total SiO2, .29% calcium, .25% phosphorus, 11.3% CP and 28% ADF. Treatments (40 lambs/treatment) consisted of a control (C), limestone to increase dietary calcium to .6% (L), L + 1% sodium bicarbonate (LS) and L + 1% ammonium chloride (LA). After a 91-d experimental period followed by a 56-d postexperimental finishing period, silica kidney deposits were found in all treatments, and SiO2 made up 74% to 97% of the urolithic ash. Kidney urolith incidences in the four treatments were C, 7/40; L, 12/40; LS, 20/40; and LA, 9/40. A higher urolith incidence in LS (LS vs C, P less than .05) and a trend toward a higher incidence in L (L vs C, P less than .2), accompanied by elevated urine pH (L = LS greater than C greater than LA, P less than .01), lend support to the concept that high-silica diets having high calcium to phosphorus ratios and alkali-forming potentials contribute to silica urolithiasis.
Stewart
S R
SR
Chem. Dept., South Dakota State University, Brookings 57007.
Emerick
R J
RJ
Pritchard
R H
RH
D000468:Alkalies / Q000378:metabolism*; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000009:adverse effects*; D004032:Diet; D008297:Male; D010758:Phosphorus / Q000008:administration & dosage / Q000009:adverse effects*; D012756:Sheep; D012757:Sheep Diseases / Q000209:etiology*; D012822:Silicon Dioxide; D014545:Urinary Calculi / Q000209:etiology / Q000662:veterinary*
D000468:Alkalies; D002136:Calcium, Dietary; D010758:Phosphorus; D012822:Silicon Dioxide