Study On The Accuracy And Correlation Of The Backfat Thickness Measurements In Live Pigs With A Mode And B Mode Ultrasonic Instruments

Probing test in Jinhua nucleus herd of Canadian Yorkshire with A mode (Renco, American)and B mode (Ami900,Canada) ultrasonic instrument simultaneity on last 3/4 rib (PI) and the joint-point of the thoracic vertebra and lumber vertebra (P2) off the mid-line 4-6cm when the pigs in their 25,50,75Kg body weight. The loin depth on the last 3/4 rib off the mid-line 4-6cm also was probed by B mode . When the pig's body weight between 25-50 kg , weighted them every week. To probe the 19 barrows (at 95.18 Kg body weight) with A mode and B mode on the two sites and after slaughter, using the caliper testing the backfat thickness on the same sites. SAS program was applied to analyze all the data to get the regression equations and to estimate the genetic parameters.The results indicated that the probe site and sex had significant effect on the backfat thickness . The PI backfat thickness thinner than P2's, the boar's thinner than the gilt's.The backfat probed by A mode and B mode existed significant linear regression. The regression equation was: the backfat thickness on PI by B mode =6.1657+1.0497 (the backfat thickness on P2 by A mode-4.07) (for the boars); the backfat thickness on Plby B mode =9.0723+0.6105 (the backfat thickness on P2by A mode -3.64) (for the gilts).The analyze of correlation shows that in the period of 25Kg live weight ,the phenotype correlation for the two sites by A mode and B mode were 0.574 and 0.579,respectively. The phenotype and genetic correlation between the 50Kg live weight and the backfat on P2 by A mode were 0.5628 and 0.0984, respectively; the phenotype and genetic correlation between the 50Kg live weight and the backfat on PI by B mode were 0.2784 and 0.2302, respectively. The phenotype and genetic correlation between the 75Kg live weight and the backfat on PI by B mode were 0.3239 and -0.3265, respectively. The phenotype and genetic correlation between the backfat on Plby A mode and the backfat on site land P2 by B mode were 0.5957and 0.335, 0.4346 and 0.74, respectively. The phenotype and genetic correlation between the backfat on Plby B mode in 50Kg live weight and in 75Kg live weight were 0.1859 and 0.247, respectively.The analyze of carcass shows that the means of the backfat on Plby A mode was 13.94?.32mm,on P2was 14.88?.93mm; the means of the backfat on Plby B mode was4315.59?.02mm, on P2were 20.79?.57mm; the means of the carcass backfat on the two sites were 21.35?.93mm and 24.29?.01mm, respectively. The phenotype correlation between the backfat on PI by A mode and the carcass's actual backfat was 0.7007, the phenotype correlation between the backfat on Plby B mode and the carcass's actual backfat was 0.8316.The accuracy of B mode is higher than A mode's.The heritability of the backfat on the two sites by A mode in 50Kg live weight were 0.366 and 0.691,respectively, for the B mode were 0.634 and 0.549, respectively. In the period of the 75Kg live weight, the heritability of the backfat on the two sites by A mode were 0.381 and 0.695, for the B mode were 0.641 and 0.564, respectively.