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Social interactions among animals raised in pens can affect their performance. In this study direct and competitive models were compared to investigate the influence of social genetic effects on variation of carcass weight (CW), carcass lean meat content (LM) and ham round shape (RS) in heavy pigs. Four sequential models including, in addition to sex and slaughter group fixed effects, the random effects of the social group, litter (full-sibs family), direct and social genetic effects of pigs were evaluated. Social group and litter effects accounted for about 4 and 3% of the phenotypic variance, respectively. When social genetic effects were added to model, a small social heritability was estimated for all traits (from 0.3 to 0.7% of the phenotypic variance). A negative correlation between direct and social effects was estimated for LM and RS, reducing the total heritable variance available for selection. Model comparison showed that the best fit was provided by the model including only direct additive genetic effects of pigs. So, this model seems still preferable for the genetic evaluation of the investigated traits.