Validation of a Model for Prediction of Percent Intramuscular Fat on Live Feedlot Cattle

A prediction model from a previous study was utilized to evaluate the degree of fit when this model is applied to an independent data set. The degree of fit was evaluated using means, regression analysis, correlation coefficient, distribution of residuals, and mean square error of prediction (MSEP). The model provided a reasonably accurate prediction of intramuscular fat with a mean bias of 0.13%. For 47.1% of the steers, percent intramuscular fat was predicted within ± 0.5%, and for 77.6% of the steers, prediction of percent intramuscular fat was made within ± 1%. Pearson product moment correlation between predicted and actual percent intramuscular fat was 0.74 (p \u3c .01), and the square root of MSEP indicated a prediction error of 0.9%

Evaluation of Ultrasound Measurements of Fat Thickness and Ribeye Area, I. Assessment of Technician Effect on Accuracy

Data from two feeding trials were used to estimate accuracy of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan taken just before slaughter. Each technician interpreted the image of an individual steer twice on two different days. Accuracy of interpretation was evaluated using simple statistical measures, including means, standard deviations, regression and correlation coefficients, RMSE, and ESD. The overall technician biases for ultrasound measurements of fat thickness and ribeye area were -0.17 cm and 0.63 cm2, respectively. Mean bias by technician indicated a similar direction and amount of bias (-0.14 vs -0.20 cm). However, bias in the measurement of ribeye area by the two technicians took an opposite direction ( -1.28 vs 2.54 cm2). In all cases, technician bias was within the acceptable range for BIF certification. Pearson product moment correlations between carcass and ultrasound measurements of fat thickness and ribeye area were 0.70 and 0.40, respectively. In general, fat thickness for 52% of the steers was measured within ±0.254 cm and for 85.2 % of the steers, fat thickness was measured within ±0.508 cm. For ribeye area, ±51.2 % and ±71.4 % of the steers had measurements within ±6.65 cm2 and ±12.99 cm2, respectively

Evaluation of Ultrasound Measurement of Fat Thickness and Ribeye Area, II. Repeatability of Measurements.

Data from two feeding trials were used to evaluate repeatability of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan. Each technician interpreted the image of an individual steer twice on two different days. Repeatability was evaluated as an intra-class correlation. Additional statistics used to evaluate repeatability were the slope and intercepts from a regression analysis, RMSE, and ESD. Ultrasound measurements of fat thickness and ribeye area were repeatable both within and across technicians. The only exception was the across-technician measurements of ribeye area, where an apparent difference in variances of measurements was observed

Validation of a Model for Prediction of Percent Intramuscular Fat on Live Feedlot Cattle

A prediction model from a previous study was utilized to evaluate the degree of fit when this model is applied to an independent data set. The degree of fit was evaluated using means, regression analysis, correlation coefficient, distribution of residuals, and mean square error of prediction (MSEP). The model provided a reasonably accurate prediction of intramuscular fat with a mean bias of 0.13%. For 47.1% of the steers, percent intramuscular fat was predicted within ± 0.5%, and for 77.6% of the steers, prediction of percent intramuscular fat was made within ± 1%. Pearson product moment correlation between predicted and actual percent intramuscular fat was 0.74 (p < .01), and the square root of MSEP indicated a prediction error of 0.9%.</p

Evaluation of Ultrasound Measurement of Fat Thickness and Ribeye Area, II. Repeatability of Measurements.

Data from two feeding trials were used to evaluate repeatability of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan. Each technician interpreted the image of an individual steer twice on two different days. Repeatability was evaluated as an intra-class correlation. Additional statistics used to evaluate repeatability were the slope and intercepts from a regression analysis, RMSE, and ESD. Ultrasound measurements of fat thickness and ribeye area were repeatable both within and across technicians. The only exception was the across-technician measurements of ribeye area, where an apparent difference in variances of measurements was observed.</p

Evaluation of Ultrasound Measurements of Fat Thickness and Ribeye Area, I. Assessment of Technician Effect on Accuracy

Data from two feeding trials were used to estimate accuracy of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan taken just before slaughter. Each technician interpreted the image of an individual steer twice on two different days. Accuracy of interpretation was evaluated using simple statistical measures, including means, standard deviations, regression and correlation coefficients, RMSE, and ESD. The overall technician biases for ultrasound measurements of fat thickness and ribeye area were -0.17 cm and 0.63 cm2, respectively. Mean bias by technician indicated a similar direction and amount of bias (-0.14 vs -0.20 cm). However, bias in the measurement of ribeye area by the two technicians took an opposite direction ( -1.28 vs 2.54 cm2). In all cases, technician bias was within the acceptable range for BIF certification. Pearson product moment correlations between carcass and ultrasound measurements of fat thickness and ribeye area were 0.70 and 0.40, respectively. In general, fat thickness for 52% of the steers was measured within ±0.254 cm and for 85.2 % of the steers, fat thickness was measured within ±0.508 cm. For ribeye area, ±51.2 % and ±71.4 % of the steers had measurements within ±6.65 cm2 and ±12.99 cm2, respectively .</p