Diurnal and daily changes in the excretion of urinary silica by Merino sheep

Abstract

Urine collected at 2-hr intervals over a 24-hr period from a group of five sheep fed on the same diet in five different ways showed considerable fluctuations in volume, pH, and silica concentration. pH values ranged from 7.8 to 4.8, and silica concentration from 830 to 110 µg/ml. The latter appeared to be inversely related to urine volume, which reached a maximum c. 12 hr after feeding.

Urine collected at 24-hr intervals for 10 consecutive days from eight sheep showed marked variations in silica concentration and specific gravity. These variations appeared to be inversely related to urine volume, and silica concentration seemed to be influenced also by daily variations in total silica excretion. Considerable differences were found in the mean values for different sheep.

The significance of these results are discussed in relation to siliceous urinary calculus formation.