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Title: DEVELOPMENT AND EVALUATION OF A REGRESSION EQUATION OF PREDICTION FOR FAT-FREE SOFT TISSUE IN HETEROGENOUS POPULATIONS OF CATTLE

Author
item Jenkins, Thomas
item Leymaster, Kreg
item Macneil, Michael

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: An accurate, precise protocol that utilizes measurements that are inexpensive to collect and does not diminish commodity value is needed to predict nonfat carcass tissue in beef cattle using carcass weight, fat depth at the 12th rib and resistive impedance as estimative traits. A prediction equation was developed that met these criteria. Parameters were estimated from a highly heterogenous population of cattle following feeding period. This equation was evaluated with an independently collected data set. Results from the evaluation demonstrated the effectiveness of use of the predictive equation. Application by researchers provides an effective means to reduce data collection cost. Industry application could provide a means to determine carcass value.

Technical Abstract: Regression equations to predict kilograms of fat-free soft tissue (the sum of water and protein from chemical analyses) were developed from data collected on 526 steers and heifers. Straightbred animals representing Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental breeds of cattle contributed to the data set. Cattle ranged in slaughter weight and age from approximately 350 to 575 kg and 1 to 23 m, respectively. Estimative traits included in the equation were warm carcass weight, fat depth at the 12th rib, and resistive impedance. Resistive impedance is the ratio of a defined carcass length (cm) and the resistance to the passage of an electrical current (ohms). Carcass soft- tissue samples were taken for determination of chemical constituents. The prediction equation accounted for 94% of the variation in fat-free soft tissue of the carcass. Adjusting for breed-sex-diet contemporary groups increased the R**2 value by 2% units. The prediction model was evaluated using data collected on 65 steers sired by Charolais or Hereford bulls at the Ft. Keogh Livestock and Range Research Laboratory, Miles City, Mt. Post-weaning feeding strategies and slaughter ages varied among these animals. Carcass weight, back fat depth, and resistive impedance measures were recorded. Carcass soft-tissue samples were taken for determination of chemical constituents. Values of estimator variables recorded at Ft. Keogh were used in the regression equation to predict fat-free soft tissue for each animal. The values for kg of fat-free soft tissue determined from chemical analysis were regressed on predicted fat-free soft tissue. Results indicate that fat-free soft tissue of carcasses can be accurately predicted using estimative traits that do not diminish carcass value.