Choice of probing site for classification of live pigs using ultrasonic measurements

Body length and ultrasonic fat thickness measurements were taken on 86 live pigs in order to find an optimal probing site for estimation of lean meat proportion. The next day pigs were slaughtered and measurements with the He nnessy Grading Probe (HGP) were made in order to estimate the lean meat pro portion. Fat thickness, 6 cm off the dorsal mid line, increased from a value of 9.5 mm at a site 4 cm cranial to the East rib, progressively through intermedia te sites to a value of 12.4 mm, 22 cm cranial to the last rib. Fat thicknes s measurements at different sites (live pigs) were highly correlated with H GP fat thickness at the site between 3rd and 4th from last rib (3/4 LR) and estimated lean meat proportion (carcasses); correlations ranged from 0.80 to 0.89 and -0.71 to -0.85 respectively The most accurate predictor of esti mated lean meat proportion from the live pig measurements was the measureme nt at 18 cm cranial to the last rib. Measurement at the site half the dista nce between the occipital bone and the base of the tail (midpoint) was the second-best for estimated lean meat proportion. Generally, this midpoint on live pigs was situated around the 3/4 LR on car casses. However, the range was considerable. Half of the number of animals had a midpoint in the range of -2.5 to 2.5 cm from 3/4 LR. The site midpoin t is easily located on the animal and the results of this study suggest tha t it can be used as an accurate predictor of estimated lean meat proportion . Therefore it can serve as the probing site for classification of live pig s.