Estimativa de parâmetros genéticos para características de carcaça em um rebanho de suínos Large White

Abstract

In order to estimate the genetic parameters of swine carcasses, data of dressing percentage (RC), carcass lenght by MBCC (CCMB), carcass lenght by the American method (CCMA), average backfat thickness (ETM), backfat thickness at 6,5 cm from the dorsal line (P2), loin eye area (AOL), lean:fat ratio (RCG) ham yield (RP), lean and fat percentages (PC and PG), lean cuts percentage (PCM), fat weight:lean weight ratio (RGC), and lean tissue growth rate (TCM) obtained from 704 swine of the Large White Breed. Heritability coefficients (H2), and genetic (rG) and phenotypic (rP) correlations were estimated by the Restricted Maximum Likelyhood Method (REML) using model which include fixed effects (sex and contemporary group), and randows (genetic and residual effects). The common litter effect was not utilized in the model, due to the small size of data file, and the detection of a confounding of the fixed and random effects. The covariables "slaughter weight" for RC and "cold carcass weight" for the other traits, were used when necessary. The estimates of H2 for RC, CCMB, CCMA, ETM, P2, AOL, RCG, RP, PC, PG, PCM, RGC, e TCM were 0,39; 0,34; 0,19; 0,17; 0,16; 0,27; 0,15; 0,12; 0,45; 0,36; 0,32; 0,39 and 0,37 respectively. ETM, P2 and RCG were the most genetically correlated traits with the carcass fat and meat contents. They showed positive correlations with PG and RGG, ranging from 0,66 to 0,92 and negative with PC and PCM ranging from -0,56 to -0,86. The AOL, CCMA and RP presented intermediary and the CCMB and RC showed little genetic correlation with those contents. In general, the same trend was observed for the phenotypic correlations. The AOL and RCG presented the gratest genetic and phenotypic correlation with the TCM showing that in addition to improving the animal's carcass quality, those classification traits enable to improve the lean production rate through selection. Onthe other hand, the carcass lenght (CCMB and CCMA) and backfat thickness (ETM and P2) had genetic correlations with TCM wich disfavor the carcass quality. With the exception of the AOL and RCG the classification traits showed not be correlated phenotypically with the TCM.