Comparison of transverse and longitudinal real-time ultrasound scans for prediction of lean cut yields and fat-free lean content in live pigs.

Abstract

Live animal real-time ultrasound scans and carcass measures were taken on 80 pigs comprising two sexes (42 barrows; 38 gilts) and two halothane genotypes (40 carriers and 40 negatives) that were slaughtered between 108 and 148 kg live weight. Transverse scans (TRUS), at right angles to the midline, were taken on right (RS) and left (LS) sides at the last rib. Longitudinal scans (LON) were taken 6.5 cm off the midline immediately anterior (ANT) and posterior (PST) to the last rib on both the RS and LS. Longissimus muscle depth and area and backfat thickness over the longissimus muscle were measured on TRUS. Backfat thickness and longissimus muscle depth were measured at each end of the LON. Backfat thickness and longissimus muscle measurements were taken at the 10th and last rib on the RS of the carcass. Carcasses were fabricated using standard techniques to establish lean cut yields and carcass soft tissue was chemically analyzed to determine fat-free lean contents. Stepwise regression analysis was performed to develop equations to predict the weights and percentages of lean cuts and fat-free lean. Fat and muscle measures taken from ultrasound scans were generally less accurate than last rib carcass measures at predicting composition. There was little difference in R2 for equations based on either TRUS or ANT/LON; however, PST/LON, generally, were less accurate than ANT/LON. Combining measurements from more than one scan gave little improvement in R2 compared with the best single scan. Estimates of sex bias for carcass composition prediction were small. Halothane genotype and carcass lean content biases were detected; equations derived from the pooled data tended to overestimate the lean content of negative pigs and fatter carcasses and underestimate the lean content of carrier animals and leaner carcasses.

Prediction of carcass lean content by real-time ultrasound in Pietrain and negative stress Pietrain

“…Those values are higher than those of this study. In contrast, according to Cisneros et al (1996), the correlation between carcass weight and longissimus muscle area in the latter study (0·43) was lower than we found.…”

“…Gresham et al (1992) reported significant correlation coefficients between live weight and longissimus muscle depth (0·41) and between hot carcass weight and longissimus muscle depth (0·47) in commercial market pigs typical of the US population 10 years ago. In the same way, the correlation between carcass harvest weight and longissimus depth was 0·36 (Cisneros et al, 1996). Those values are higher than those of this study.…”

“…Alliston et al (1982) evaluated two early designs of ultrasound scanning equipment and concluded that including longissimus muscle area measurements with live weight and P2 backfat thickness at the last rib did not improve the precision of estimating carcass lean content. On the other hand, the findings of Molenaar et al (cited by Cisneros et al (1996)) indicated that the accuracy of proportion of lean cuts predicted from real-time ultrasonic scans was significantly improved by including longissimus muscle measurements (depth or area) together with backfat thickness in prediction equations. This was in agreement with the results of the present study.…”

“…The difference observed with the trial results of Gresham et al (1992) could be dependent on ultrasound technology or on genetic and compositional variation for animals used in each trial. Carcass lean proportion was slightly correlated with longissimus muscle depth (0·41) and with longissimus muscle area (0·47) in the study of Cisneros et al (1996). According to Courchaine et al (1996), correlations between lean cuts and longissimus area varied from -0·28 to 0·15.…”

“…Gresham et al (1994) suggested that a single longitudinal scan taken at the 10th rib was accurate for predicting carcass composition but did not include scans at other positions. Equations based on ultrasound scans have been shown to explain more variation of the dependent variables than those based on direct carcass measurements taken at the last rib (Terry et al, 1989;Cisneros et al, 1996). There are few reports in the literature for regression equations predicting carcass composition separately for the different halothane genotypes.…”