A COMPARISON OF BLOOD CHARACTERISTICS AND BACKFAT THICKNESS AS PREDICTORS OF CARCASS COMPOSITION OF MARKET WEIGHT PIGS

Abstract

Live animal measurements of backfat and several blood characteristics were compared as predictors of percent protein and fat in dressed carcasses of barrows and gilts. There was a distinct sex difference in the relationship between certain blood characteristics and carcass composition. In the gilts (n = 21), red cell volume and hemoglobin were significantly correlated with percent protein (0.633 and 0.615, respectively) and percent fat (−0.497 and −0.474, respectively), while in the barrows (n = 23) the correlations were not statistically significant. Backfat by probe was significantly correlated with percent protein and fat in the carcasses of both barrows (−0.597 and 0.644, respectively) and gilts (−0.584 and 0.563, respectively). The most important factor, as determined by stepwise multiple regression, in predicting percent protein in gilts was red cell volume, no other variable reducing the residual sums of squares further. In barrows, percent protein was best predicted by backfat thickness, blood characteristics reducing the residual sum of squares an additional 20%. In both sexes backfat thickness was the most important factor in predicting percent fat, red cell volume contributing an additional 7.4% to the prediction in gilts. While blood characteristics proved to be a useful adjunct to the probe in predicting carcass composition in barrows, they added little to the prediction of percent protein and fat in gilts. Since blood characteristics are more difficult to measure than backfat thickness, probing should remain the most practical means of predicting carcass composition in the live animal.