The aim of the study was to estimate correlations between fattening and slaughter traits of gilts and their subsequent reproductive performance. A total of 5468 Polish Landrace gilts from nucleus farms were studied. Daily gain and selection index were positively correlated (0.14-0.22) with the number of piglets born and reared in successive litters. For the other traits, the correlations with reproductive traits were close to zero. The phenotypic correlations obtained between fattening and slaughter performance traits and subsequent reproductive performance of gilts are in most cases indicative of the low relationship between these traits.

In recent years, intensive attention has been put on improving reproductive performance of pigs. Several experiments aimed to identify markers associated with prolificacy, but this issue still remains open. In our study, we investigated associations between polymorphisms in IGF2, GNAS and MC4R genes with reproductive traits of Polish Landrace and Large White pigs. We did not find any significant associations for g. GNAS314T > 324C, IGF2 intron3-g.3072G > A or g. MC4R 1426G > A in Polish Landrace and Large White pigs. In the case of IGF2 intron3-g.3072G > A, this information is of great importance, because this marker is widely implemented in pigs breeding and previous experiments suggested its role in prolificacy of pigs. We also investigated expression of IGF2 gene and showed that this gene is monoallelically expressed in reproductive organs (ovary and cornus uteri).

The polymorphisms of LEPR and MC4R genes are involved in appetite control mechanisms and indirectly associated with level of fat content in pig carcasses. Therefore, the aim of our study was to determine if both polymorphisms have an effect on components of colostrum and milk of sows. In our study we used gilts of two Polish breeds: Polish Landrace and Polish Large White, which belong to dam-line in Polish breeding. Colostrum and milk of sows were collected in 7, 14 and 21 day of lactation to assay solids, total protein, fat and lactose. The obtained results showed, that the observed mutation (G/A 1426 MC4R ) had a significant effect mainly on the fat and solids content of colostrum. Animals with the MC4R AA genotype had 2.13 and 1.91 % ( P ≤ 0.01) lower fat content of colostrum compared to sows with the MC4R GG genotype and heterozygous MC4R AG . The presence of the MC4R A allele in the animals’ genotype contributed to a decrease in fat and solids content of colostrum. The LEPR /HpaII mutation was found to have a considerable effect on the level of most colostrum components (fat, protein and solids) in both pig breeds. Significant decrease in the value of the colostrum components (except lactose) was observed only for animals with the allele LEPR B . The results obtained suggest that these genes might be used in selection of dam-line pigs as genetic markers of milk quality.