Physical studies of the alimentary tract of grazing cattle

Abstract

Two sets of twin cows were used to compare the following methods of measuring the volume of water in the reticulo-rumen (fluid volume) :— 1. (i) directly, by removing the digesta from the reticulo-rumen; 2. (ii) indirectly, by dosing with polyethylene glycol (PEG) and following its disappearance curve from the reticulo-rumen; 3. (iii) indirectly, from body weight, by using information gained from (i) above on variations in empty body weight (i.e., weight after removing the digesta). The direct measurements were simple, rapid. and presumably accurate. During experiment I, PEG measurements showed no significant bias when compared with direct measurements, but standard errors of mean differences between PEG and direct measurements were relatively large. During experiment II, a modified technique gave PEG measurements which were more consistent (standard errors were smaller), but in two cows PEG measurements were significantly lower than direct measurements. The differences between fluid volumes obta...