GENETIC-PARAMETERS OF BACKFAT THICKNESS, AGE AT 100-KG AND ULTIMATE PH IN ON-FARM TESTED FRENCH LANDRACE AND LARGE WHITE-PIGS

Genetic parameters of age (AGE) and average backfat thickness (ABT) at 100 kg, as well as of ultimate pH of Adductor femoris (pH(ad)), Semim embranosus (pH(sm)) and Semispinalis (pH(ss)) muscles, were estimated for the Large White (LW) and French Landrace (LF) breeds using a deriv ative free Restricted Maximum Likelihood (DF-REML) procedure applied t o a multiple trait individual animal model. The data consisted of 2456 9 LW and 13360 LF pigs tested for AGE and ABT in 35 selection herds be tween 1989 and 1992, among whom 6358 LW and 3538 LF animals were slaug htered and measured for pH. Heritabilities of AGE, ABT, pH(ad), pH(sm) and pH(ss) are, respectively, 0.25; 0.45; 0.22; 0.17; 0.22 in the LW breed and 0.23; 0.55; 0.13; 0.14; 0.18 in the LF breed, with standard errors ranging from 0.01 to 0.02. AGE and ABT exhibit slightly negativ e genetic correlations in LW (-0.12+/-0.03) and LR (-0.07+/-0.04) bree ds. Low positive genetic correlations are obtained between AGE or ABT and the three ultimate pH measurements in the LW breed (from 0.01 to 0 .20). These same genetic correlations are more variable in the LF bree d (from -0.20 to 0.18).