GENETIC-PARAMETERS OF LITTER TRAITS IN 3 PIG BREEDS IN SOUTHERN BRAZIL

This paper reports estimates of genetic parameters for litter traits, obtained in three pig breeds in southern Brazil. A sample of 7064 Larg e White (LW), 4538 Landrace (LR), and 2400 Duroc (DC) litters was anal yzed with a mixed model that included a set of fixed effects (farm, mo nth and year of parity, and age of sow at parity) and the random effec ts of boar within farm, and daughter within hear. Each sow farrowed at least two litters. Heritability estimates and corresponding standard errors were: (1) total number of piglets born, 0.062 +/- 0.023 (LW), 0 .121 +/- 0.033 (LR), and 0.078 +/- 0.044 (DC); (2) number of piglets b orn alive, 0.060 +/- 0.023 (LW), 0.119 +/- 0.033 (LR), and 0.073 +/- 0 .043 (DC); (3) piglets alive at day 21, 0.075 +/- 0.024 (LW), 0.101 +/ - 0.031 (LR), and 0.083 +/- 0.044 (DC); (4) litter weight at birth, 0. 151 +/- 0.30 (LW), 0.155 +/- 0.037 (LR), and 0.109 +/- 0.048 (DC), and ; (5) litter weight at day 21, 0.133 +/- 0.028 (LW), 0.143 +/- 0.035 ( LR), and 0.174 +/- 0.056 (DC). The LR breed had the greatest amount of genetic variability for litter size traits and in general, the herita bilities of litter weight traits had larger values than those of litte r size traits. The genetic correlations among the five traits, with th ree exceptions, were high, suggesting the presence of favourable pleio tropic effects. These high correlations also reflect the part-whole re lationships among traits.