Submitted to: Professional Animal Scientist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2004
Publication Date: 6/1/2004
Citation: Aiken, G.E., Rouquette, Jr., F.M., Tabler, S.F., Looper, M.L. 2004. Prediction of future carcass traits in stocker cattle at the conclusion of grazing. Professional Animal Scientist. 20:246-254. Interpretive Summary: Prediction of eventual carcass traits for stocker cattle at the conclusion of grazing could provide cattleman and feedyard managers with a valuable tool for culling, co-mingling of animals, feedlot pen assignments, and making management decisions. Pens of feedyard cattle that are uniform in body weight and carcass characteristics can enhance the profitability of retained ownership of cattle. Ultrasonic measures of 12th to 13th rib fat thickness and ribeye area were combined with information on breed type and gender, and measures of body weight and condition to determine if economically important carcass traits (percentage and pounds of retail product, hot carcass weight, and quality grade) can be predicted for cattle entering the feed yard. Breed type and number of days on feed in the feedyard showed to be the most relevant information, and models that combined this information with measures of backfat and body weight showed promise to make economically relevant predictions. Further model development is needed to increase the robustness of models and improve the accuracy and precision of the prediction models.
Technical Abstract: Prediction of eventual carcass traits for stocker cattle at the conclusion of grazing could be useful for culling, co-mingling of animals, feedlot pen assignments, and making management decisions in the feedyard. Ultrasound measurements of 12th to 13th rib longissimus muscle area and fat thickness, and off pasture body weights were collected from yearling cattle at the conclusion of grazing in two experiments that evaluated stocking rate and grazing management effects on rye-annual ryegrass pastures. Correlations were analyzed to determine relationships between carcass traits and ultrasound measures, body condition measure, and off-pasture body weights. Ultrasound measures breed type, gender, and feedlot days on feed were evaluated in multiple regression models to determine if these variables influence eventual carcass percentage retail product, kg retail product, and hot carcass weight, and marbling score. Ultrasound FAT and body condition were negatively correlated with percentage retail product, kg retail product, and hot carcass weight, and were positively correlated with marbling score. All reduced regression models has R^2 values between 0.15 and 0.63, and models with inputs of ultrasound fat thickness and off-pasture body weight consistently had the numerically highest R^2 values and lowest RMSE. Multiple regression analysis indicated that prediction of carcass traits from stocker cattle ultrasonic measurements at the conclusion of grazing were possible, but improvement in the models will be necessary to reduce error and improve reliability.