Genetic markers associated with resistance to infectious diseases have no effects on production traits and haematological parameters in Italian Large White pigs

Infectious diseases have large economic impacts on the pig breeding industry worldwide. A few genetic markers associated to disease resistance have been recently identified and used in marker-assisted selection (MAS) in a few pig populations, as part of disease control programs. Neonatal Diarrhea (ND), Post-weaning Diarrhea (PWD), caused by enterotoxigenic E. coli, and Porcine Reproductive and Respiratory Syndrome, caused by PRRS virus (PRRSV), are diseases with high priority for the pig industry. Since interactions or antagonism between growth, innate immunity and disease resistance traits could exist, this work investigated if four disease resistance gene markers [mucin 4 (MUC4), rs338992994 associated with resistance to ND; fucosyltransferase 1 (FUT1), rs335979375 associated with resistance to PWD; and guanylate binding protein 1 (GBP1), rs340943904 and rs80800372 (also known as WUR10000125) associated with resistance to PRRS] could affect seven production traits (average daily gain, back fat thickness, lean meat cuts, feed gain ratio, ham weight, visible intermuscular fat and ham weight loss at first salting) and 15 haematological parameters in about 550 performance tested Italian Large White pigs. We also monitored allele frequencies of the same markers on Italian Large White boars sampled under the national selection breeding program over a 20 years-period. Moreover, we evaluated allele frequencies of these polymorphisms in four Italian local pig breeds (Apulo-Calabrese, Casertana, Cinta Senese and Nero Siciliano). The frequency of the resistance-associated alleles for the four polymorphisms was usually higher in all local pig breeds, indirectly supporting a higher rusticity of autochthonous breeds, compared to commercial populations. The two GBP1 polymorphisms were not in complete linkage disequilibrium in all breeds, except in Apulo-Calabrese. No significant allele frequency change for the investigated markers occurred over 20 years in the Italian Large White boar population in three of these markers. Only FUT1 showed a modest but significant change of allele frequencies over this period. Association analyses carried out in Italian Large White pigs for production traits, meat quality or haematological parameters under investigation showed no significant effect of any genotyped polymorphisms. Our results indicate that implementing MAS programs in Italian Large White pigs with polymorphisms associated with disease resistance have no direct effects on production traits. The selection program running for this heavy pig breed might not negatively impact disease resistance derived by the investigated major genes.