Genomic Analysis of IgG Antibody Response to Common Pathogens in Commercial Sows in Health-Challenged Herds

Abstract

Losses due to infectious diseases are one of the main factors affecting productivity in the swine industry, motivating the investigation of disease resilience-related traits for genetic selection. However, these traits are not expected to be expressed in the nucleus herds, where selection is performed. One alternative is to use information from the commercial level to identify and select nucleus animals genetically superior for coping with pathogen challenges. In this study, we analyzed the genetic basis of antibody (Ab) response to common infectious pathogens in health-challenged commercial swine herds as potential indicator traits for disease resilience, including Ab response to influenza A virus of swine (IAV), Mycoplasma hyopneumoniae (MH), porcine circovirus (PCV2), and Actinobacillus pleuropneumoniae (APP; different serotypes). Ab response was measured in blood at entry into gilt rearing, post-acclimation (∼40 days after entering the commercial herd), and parities 1 and 2. Heritability estimates for Ab response to IAV, MH, and PCV2 ranged from 0 to 0.76. Ab response to APP ranged from 0 to 0.40. The genetic correlation (r G) of Ab response to IAV with MH, PCV2, PRRSV, and APP mean (average Ab responses for all serotypes of APP) were positive (>0.29) at entry. APP mean was negatively correlated with PCV2 and MH at entry and parity 2 but positively correlated with MH at postacclimation and parity 1. Genomic regions associated with Ab response to different APP serotypes were identified on 13 chromosomes. The region on chromosome 14 (2 Mb) was associated with several serotypes of APP, explaining up to 4.3% of the genetic variance of Ab to APP7 at entry. In general, genomic prediction accuracies for Ab response were low to moderate, except average Ab response to all infectious pathogens evaluated. These results suggest that genetic selection of Ab response in commercial sows is possible, but with variable success depending on the trait and the time-point of collection. Future work is needed to determine genetic correlations of Ab response with disease resilience, reproductive performance, and other production traits.

Genetic and phenotypic indicator traits for reproductive performance in commercial sows

“…Animals were not voluntarily infected with any of the pathogens in the study; therefore, the level of exposure (if any) to these antigens was inconsistent. In our previous work, %seroconverted datasets were created based on diagnostic thresholds of ≥ 0.4 for PRRSV, APP, MH, ≥ 0.6 for IAV, and 0 for PCV2 (Sanglard et al, 2020b). Within each CG, %seroconverted datasets were obtained for five levels: 0, 25, 50, 75, and 100%, representing 0 to <25%, 25 to <50%, 50 to <75%, 75 to <100%, and 100% of the animals being positive for each of the pathogens analyzed, respectively.…”

“…Within each CG, %seroconverted datasets were obtained for five levels: 0, 25, 50, 75, and 100%, representing 0 to <25%, 25 to <50%, 50 to <75%, 75 to <100%, and 100% of the animals being positive for each of the pathogens analyzed, respectively. We followed Sanglard et al (2020b) and used the %seroconverted datasets per pathogen and time-point combination with the highest h 2 (Additional file 10.2). For all APP serotypes, there were only a few positive animals in the whole dataset; hence, %seroconverted datasets were not created.…”

“…for individual APP serotypes were low, while APPmean showed moderate to high h 2 (Sanglard et al, 2020b). Hence, in this study, we analyzed only APPmean.…”

“…Hence, in this study, we analyzed only APPmean. In addition, as proposed by Sanglard et al (2020b), we calculated the mean of standardized antibody response (S/P ratio divided by their respective standard deviation within each trait) to all infectious pathogens (MEAN, with S/P ratio values expressed as S/PMEAN) to use an additional trait in the analysis.…”

“…In our previous work, we have reported that the genetic variability of antibody response to infectious pathogens in commercial sows increases with the proportion of positive animals in the dataset, although large variability in results existed depending on the time of antibody response data collection (Sanglard et al, 2020b). Nonetheless, although some studies have reported that antibody response is correlated with reproductive performance, these have focused on only a few pathogens.…”