Identification of genetic markers for productive life in commercial sows1

Abstract

Escalating replacement rates and production costs warrant attention on sow productive life (SPL). Increasing average SPL by one-tenth of 1 parity would result in an annual revenue increase of over $15 million in the United States. Research in model organisms has revealed conserved genes and gene pathways that lead to longer lifespan. The most prominent gene pathways are those involved in growth, most notably genes in the IGF pathway that serve to mimic the response of caloric restriction. The objective of this research was to test the hypothesis that these well conserved genes and gene pathways could also play a role in SPL, even though the productive life of sows is both a measure of longevity and their reproductive performance. Preliminary research on 3 distinct populations of over 2,000 animals suggested that several genes were associated with components of SPL. Genetic markers were then analyzed against the corresponding records of the sows for reproductive and longevity traits using a validation population of 2,000 commercial females. Right censored data were used to test associations of genetic markers with survival to defined time points. Three distinct models of survival analysis were implemented using nonparametric estimates of the survival distribution in a sequential order, using a parametric accelerated failure time model with a Weibull distribution of the error term, and a Cox proportional hazards model, which is a semiparametric model that uses an unspecified baseline hazard function. The genetic markers CCR7 and CPT1A were significantly associated (P < 0.05) with survival using the nonparametric model and tended (P < 0.1) toward significance using the parametric and semiparametric models with significantly different effects (P < 0.05) between some genotype classes. Genetic markers for MBL2, IGFBP3, and WARS2 also tended (P < 0.1) toward significance for survival traits, but were not consistent. Mixed model analyses were used to determine the associations of these genetic markers with reproductive traits. The genetic markers for IGFBP1, MBL2, CPT1A, CCR7, SLC22A5, and ACE were significantly (P < 0.05) associated with at least 1 reproductive trait. These results show that molecular markers should be considered for use in marker-assisted selection to improve SPL. ABSTRACT: Escalating replacement rates and production costs warrant attention on sow productive life (SPL). Increasing average SPL by one-tenth of 1 parity would result in an annual revenue increase of over $15 million in the United States. Research in model organisms has revealed conserved genes and gene pathways that lead to longer lifespan. The most prominent gene pathways are those involved in growth, most notably genes in the IGF pathway that serve to mimic the response of caloric restriction. The objective of this research was to test the hypothesis that these well conserved genes and gene pathways could also play a role in SPL, even though the productive life of sows is both a measure of longevity and their reproductive perfor...

Effect of polymorphisms in candidate genes on reproduction traits in Finnish pig populations1

“…Initial analysis of American Yorkshire and Landrace populations indicated that several markers were significantly associated with either sow survival or reproductive traits (Mote et al, 2009). Markers selected from these preliminary data were evaluated in 2 Finnish pig populations.…”

“…In a recent association analysis (Mote et al, 2009), the most promising markers for sow survival were within genes C-C chemokine receptor 7 (CCR7) and CP-T1A. The CPT1A gene codes for an enzyme involved in the transport of certain long-chain fatty acids into mitochondria, a process essential to the production of ATP.…”

“…As in the Landrace population, the beneficial allele 2 was also the major allele in this population (frequency of 0.79); therefore, selection for this marker would not have a major impact on these populations. Another IGFBP marker demonstrating a moderate association with sow survival was recently detected in the IGFBP3 gene (Mote et al, 2009). In the Finnish Yorkshire population, this marker was moderately associated with farrowing interval in later parities (0.5-d shorter interval for sows carrying allele 1).…”

“…Results with P < 0.05 were considered significant. This method does not allow for multiple testing, but the focus of this article was to validate the previous positive findings (Mote et al, 2009), rather than to test a random set of SNP.…”

“…Polymorphisms within genes that lead to a longer lifespan and reproduction defects in model organisms have been tested for associations with survival and prolificacy traits in American Yorkshire and Landrace populations (Mote et al, 2009). Significant correlations with litter size have been detected using SNP within the genes IGFBP1, SLC22A5 [organic cation/carnitine transporter 2 (solute carrier family member I), OCTN2], and CPT1A (carnitine O-palmitoyltransferase I).…”