Renal Function of Cattle under Various Water and Salt Loads

Abstract
Effects of water loading, sodium chloride loading and 4 days total fasting on kidney function were studied in growing Hereford heifers. Water diuresis did not affect the urine excretion of urea-N or total nitrogen. Peak urine flow occurred between 2 and 4 hr. following drenching. Water drenching did not affect glomerular filtration rate. When the drinking water contained 1.0% NaCl, the urinary excretion of urea-N was increased 37.1% over that of heifers drinking tap water ad libitum, even though feed intake was unchanged. This may be an osmotic effect, since a correlation of 0.81 was observed between osmolal clearance and total urine urea-N excretion. Hypertonic NaCl (1.5%) drinking water increased the ratio of urine excretion to water intake from 0.31 during euhydration to 0.82 during salt loading. Plasma osmolality increased from control values of 291 to 332 mOsm./kg. during salt loading, and there was marked hypernatremia. Urine sodium excretion increased approximately ten-fold; however, there was no increase in urine osmolality. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science

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