Association between cathepsin L (CTSL) and cathepsin S (CTSS) polymorphisms and meat production and carcass traits in Italian Large White pigs.

The aim of this work was to identify and analyse DNA markers in two cathepsin genes, cathepsin L (CTSL) and cathepsin S (CTSS), and study their association with meat quality parameters (including cathepsin activity of post mortem muscle) and several production traits in Italian Large White pigs. In silico analysis of the porcine CTSL and CTSS genes identified two new single nucleotide polymorphisms (SNPs), one located in exon 5 (CTSL) and one positioned in the 5'-untranslated region (CTSS). Allele frequencies of these two SNPs were evaluated in 7 different pig breeds. In addition, radiation hybrid mapping localized the CTSS gene on porcine chromosome 4, in an important QTL region for meat and fat deposition. Association analysis with meat quality traits, carried out in 268 Italian Large White pigs, indicated association of the CTSL polymorphism with average daily gain (ADG), weight of lean cuts (LC) and back fat thickness (BFT) estimated breeding values (P<0.05). Results for LC and BFT were also confirmed using a selective genotyping approach in other Italian Large White pigs (P<0.01). In the 268 Italian Large White pigs, the CTSS polymorphism was associated with feed:gain ratio and ADG (P<0.05). No association was observed between the analysed markers and meat quality parameters (pH(1), pH(u), lactate, glycogen, glycolytic potential and cathepsin activity, all measured on Musculus semimembranosus). Overall these results, together with those previously reported for other genes of this family, suggest that cathepsin genes play a role in defining economically important traits in pigs.