Exploring Phenotypes for Disease Resilience in Pigs Using Complete Blood Count Data From a Natural Disease Challenge Model.

Xuechun Bai,Catherine J Field,Graham S Plastow,Frédéric Fortin,Zhiquan Wang,John C S Harding,Michael K Dyck,Piggen Canada,Jack C M Dekkers,Austin M Putz

doi:10.3389/fgene.2020.00216

Abstract

Disease resilience is a valuable trait to help manage infectious diseases in livestock. It is anticipated that improved disease resilience will sustainably increase production efficiency, as resilient animals maintain their performance in the face of infection. The objective of this study was to identify phenotypes related to disease resilience using complete blood count (CBC) data from a wean-to-finish natural disease challenge model, established to mimic the disease pressure caused by many common pathogens at the commercial level of pig production. In total, 2433 F1 crossbred (Landrace × Yorkshire) barrows that went through the natural disease challenge model were classified into four groups (resilient, average, susceptible, and dead) based on their divergent responses in terms of growth and individual treatment. Three sets of blood samples for CBC analysis were drawn at 2-weeks before, and at 2- and 6-weeks after the challenge: Blood 1, Blood 3, and Blood 4 respectively. CBC of Blood 1 taken from healthy pigs before challenge did not show differences between groups. However, resilient animals were found to be primed to initiate a faster adaptive immune response and recover earlier following infection, with greater increases of lymphocyte concentration from Blood 1 to Blood 3 and for hemoglobin concentration and hematocrit from Blood 3 to Blood 4, but a lower neutrophil concentration from Blood 3 to Blood 4 than in susceptible and dead animals (FDR < 0.05). The CBC traits in response to the challenge were found to be heritable and genetically correlated with growth and treatment, which may indicate the potential for developing CBC under disease or commercial conditions as a phenotype in commercial systems as part of developing predictions for disease resilience.

Highlights

Disease resilience is defined as an animal’s ability to maintain a relatively undepressed performance in the face of infection (Albers et al, 1987; Mulder and Rashidi, 2017)
The discovery of a polymorphism at bp 307 (G/A) in the fucosyltransferase gene (FUT1) associated with susceptibility/resistance to infection with F18 fimbriated Escherichia coli (ECF18) made it possible to select for ECF18 resistant pigs (Meijerink et al, 1997, 2000)
For the data used in this study, every batch was confirmed to have been exposed to porcine reproductive and respiratory syndrome virus (PRRSV) in the test station based on randomly sampling of blood from a subset of individuals for RT-PCR 4 weeks post-challenge and enzyme-linked immunosorbent assay (ELISA) 6 weeks post-challenge

Summary

Introduction

Disease resilience is defined as an animal’s ability to maintain a relatively undepressed performance in the face of infection (Albers et al, 1987; Mulder and Rashidi, 2017). Pigs that are homozygous for the resistant allele are resistant to ECF18 due to the non-adhesion of ECF18 in the small intestine (Meijerink et al, 1997; Bao et al, 2012). Such complete resistance to a pathogen is not common, and selection for resistance to a specific pathogen may have unfavorable consequences for other production traits (Wilkie and Mallard, 1999; Guy et al, 2012). Selective breeding for resilient animals that can maintain a relatively undepressed performance in a commercial system that typically harbors abundant infectious agents could be a pragmatic way to help maintain or even improve the productivity of the swine industry

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Conclusion