Prediction of the body composition of live cattle

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Abstract
SUMMARY: Two methods of determining body composition in live cattle have been compared with the composition of the cattle as determined by chemical analysis. Total body water (TBW) was estimated from tritiated water (TOH) dilution, and circulating redcell volume (RCV) estimated from measurements of plasma volume and haematocrit. TBW was very closely related to fat-free weight and fat weight as a percentage of live weight (LW) in eight cattle ranging from 3 to 34% fat. TOH space was more precise than RCV in the estimation of the various chemical fractions of the live animal.TOH injected intravenously equilibrated with ruminal water in 8–10 h; one could be confident that equilibration had occurred 10 h after injection, and equilibration time was not affected by previous restriction of feed and water. The mean biological half life of TOH was 4·2 ± 0·4 days. Equations are presented for the practical determination of the various compartments.