Abstract
The share of variance components and correlations between the most important sow production traits (namely duration of fattening - DF, backfat thickness - BF and number of liveborn piglets - NBA) included in the pig breeding selection programme of the Republic of Serbia were estimated in this paper. The litter size at repeated farrowings (NBA1,..., NBA6) was treated as a separate trait (the multi-trait model), whereas the litter size at birth was treated as a trait repeated a number of times (the repeatability model)). The estimation of dispersion parameters was performed using the Restricted Maximum Likelihood (REML) method. The heritability of DF accounted for 23.5%, i.e. 23.3% depending on the model used, whereas BF accounted for 40.4% in both cases. The heritability of the litter size in consecutive farrowings (the multi-trait model) were in intervals ranging between 0.104 (NBA1) and 0.136 (NBA5). The heritability of NBA in the repeatability treatment accounted for 0.106, whereas the common litter environment and the permanent sow influence contributed to the total variability with 1.1% and 5.6%, respectively. Genetic correlations between the traits examined were not determined, with the exception of consecutive farrowings in the multi-trait treatment of the litter size. The genetic correlations recorded in this case proved positive and complete, with the exception of the correlation between the first and subsequent farrowings (farrowings 3 to 6) and the correlation between the second and the last farrowings (farrowings 5 and 6), which proved very strong.