ESTIMATION OF EMPTY BODY-WATER IN STEERS BY UREA DILUTION

  • 1 January 1984
    • journal article
    • research article
    • Vol. 48  (1) , 29-34
Abstract
Urea dilution has been proposed as a practical method for estimating body composition in live cattle. The urea dilution technique was evaluated by comparing urea space to direct measurement of empty body water in steers, and prediction equations were developed for empty body water in live steers using urea space parameters. Urea space was determined in 68 mixed-breed and 50 Angus steers ranging in live weight from 210-517 kg by the measurement of change in plasma urea N concentration before and 12 min after the midpoint of an i.v. infusion of 130 mg urea (20% solution w/v [weight/volume] in 0.9% saline infused over 2 min) per kg live weight. Water in ground samples from carcass and digesta-free non-carcass fractions was determined by lyophilization. Linear relationships for pooled data of both groups of steers existed between empty body water and urea space (r = 0.96, P < 0.001). Prediction of empty body water in live steers was improved by including live weight as an independent variable in a multiple regression equation (Sy.cntdot.x = 7.2 kg for pooled data). Live weight alone predicted empty body water with a standard error of the estimate 36% larger than the multiple regression prediction using urea space and live weight.