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Abstract
Information on genetic markers related to reproductive traits in pig is now available for selection scheme in practice. To verify the association between markers and traits of interest, general linear model included genotype, breed group of sow, year-season of farrowing and parity as fixed effects, and random effect was residual. Genetic markers of ESR and LEP genes were significantly associated to litter size (LS), mummified piglets (MM) and weaning to estrus interval (WEI) of purebred Landrace and Yorkshire sows in a Thai commercial population while the ADIPO and PEG1 genes were not affected to the studied traits. The ESR genotypes significantly influenced only LS (p=0.026). Genotypes of the LEP gene affected LS (p=0.022), MM (p=0.038) and WEI (p=0.027). Significant effects of additive and dominance were found only in LEPI gene. Addition of T allele decreased MM (p = 0.013), but increased WEI (p=0.009). However, the heterozygous CT was found to increase in LS (p=0.009). Landrace sows produced higher LS than Yorkshire. The first parity sows produced small LS and prolong WEI. The difference of year-season of farrowing had significant influence on STB only (p<0.001). For this population, the ESR and LEP genes could be considered in marker assisted selection program for genetic improvement and overall economic returns of sow reproduction.
Keywords: genetic marker, litter size, pre-weaning loss, non-productive days, pig
Introduction
Reproductive performance of individual sows is mostly used as an indicator for breeding herd efficiency. However, the improvement in reproductive traits is limited by traditional selection due to low heritability. Using genetic marker in breeding program could allow the inheritance of selected genes located on segments of chromosomes to be traced from parents to their offspring. The swine estrogen receptor (ESR) locus was discovered as a genetic marker for increasing litter size (LS) by Rothschild et al. (1991). This marker has been applied in commercial level to increase the number of piglets, while other genes such as Adiponectin (ADIPO) also play an important role in reproductive functions. This gene was found to involve lipid and glucose metabolism and regulation of placenta function. Its polymorphism was also related to the difference in number of mummified (MM) and stillborn piglets (Houde et al., 2008). A similar effect was found in paternal expression gene...