Nutritional effects on potassium space estimates in sheep.

p REVIOUS work at this laboratory has indicated that the short half-life isotopes '~4Na and 42K could be used in dilution experiments for the prediction of various body components such as fat-free tissue in live sheep (Lynch et al., 1965a). The use of this method appeared to contain an unacceptable error of prediction, particularly in the estimation of potassium space. This error might possibly be attributed to several factors such as the inefficiency of the detection of 3'-decay o; the potassium isotope, inequitable distribution of labeled potassium with body pools of the natural element and naturally high intakes of potassium from forages consumed by the ruminant. Since the intake of potassium could be readily adjusted, it was of interest to know how potassium space estimates in the sheep could be affected by changes in the intake of feeds containing widely different potassium levels. Feeds containing various ratios of hay: grain were chosen. The purpose of this experiment was to study the effects of feeding various ratios of hay:grain on the sodium and potassium balances and potassium space estimates in sheep.