The use of tritiated water, 4-aminoantipyrene andN-acetyl-4-aminoantipyrene for the measurement of body water in living pigs

Abstract

I . Body water content was estimated in sixteen pigs at each of three weights 27.55 and go kg with tritium, 4-aminoantipyrene (4-AA) and N-acetyl-4-aminoantipyrene (NAAP). The values obtained were compared with chemical analysis of the whole carcass. 2. The tritium method estimated total body water content accurately at 27 kg live weight but overestimated it by approximately 10% at both 55 and 90 kg live weight. 3. Antipyrene was eliminated from the pig at a rate of 55 %/h and could not be used for body water estimations. 4. Measurements with NAAP on nine pigs tended slightly to underestimate total body water content. Estimates with 4-AA showed no association with the values obtained by chemical analysis.In many nutritional studies on the effect of diet on the performance of pigs, growth rate and food conversion are the criteria used, but changes in body composition are of importance, since it has been shown that changes can occur while growth rate remains unaltered (Jones, Hepburn, Cadenhead & Boyne, 1962; Bayley, 1963).Recently Elsley & McDonald (1964) have shown that changes in the plane of nutrition, that is mainly in the energy intake, of pigs bring about changes in the rate of fat deposition while the proportions of bone and muscle remain constant when measurements are expressed on the basis of the fat-free weight. The fat and water components of the body are closely and negatively correlated (Hornicke, 1959; Kay, 1963), and therefore estimates of body water can be used to provide estimates of fat.The use of the dilution technique for the measurement of body water has been investigated in many species and various solutes have been tried. The most common solutes are tritiated water CH,O) (