Estimation of Fat-Free Soft Tissue in Lamb Carcasses by use of Carcass and Resistive Impedance Measurements

Abstract

Equations for estimating kilograms of fat-free soft tissue (sum of chemical protein and water) were developed from data collected on 40 crossbred lamb carcasses (½ Columbia-¼ Suffolk-¼ Hampshire). Estimative traits were chilled carcass weight, longissimus area, fat depth at the 12th rib and the fourth sacral vertebra, carcass length and resistive impedance. Resistive impedance estimates body composition by measuring the reduction in current as electricity passes through a carcass. The significance of fitting estimators individually or in combination was determined after statistical adjustment for variation in carcass weight. Mean slaughter weight of the lambs was 43.9 kg and mean chilled carcass weight was 20.8 kg. Fat-free soft tissue averaged 15.4 kg. At constant carcass weight, neither carcass length nor longissimus area significantly reduced variation in fat-free soft tissue. Fat depth at the 12th rib and fourth sacral vertebra explained 24 and 39%, respectively, of the variation in fat-free soft tissue among carcasses of equal weight. At a constant carcass weight, unattributed variation in fat-free soft tissue was reduced approximately 28% through use of resistive impedance measurements. Greater reduction in residual variation was realized by simultaneously fitting carcass and resistive impedance measurements. Residual variation in fat-free soft tissue was reduced 51% by fitting values for resistive impedance and fat depth at the fourth sacral vertebra. The need for accurate and precise equations to predict fat-free soft tissue for application in industry and research is discussed.