Pig peripheral blood mononuclear leucocyte subsets are heritable and genetically correlated with performance

Abstract

Indicator traits used to select pigs for increased resistance to infection or improved health must be heritable and, preferably, be associated with improved performance. We estimated the heritability of a range of immune traits and their genetic and phenotypic correlations with growth performance. We measured immune traits on 589 pigs and performance on 1941 pigs from six farms, three of which were classified as 'high health status' (i.e. specific pathogen-free) and three were of lower health status. All pigs were apparently healthy. Immune traits were total white blood cells (WBC), and peripheral blood mononuclear leucocyte (PBML) subsets positive for CD4, CD8a, gamma delta (gd) T cell receptor, CD11R1 (natural killer cell marker), B cell and monocyte markers at the start and the end of standard growth performance tests. At both time points, all immune traits were moderately to highly heritable except for CD8a 1 cells. At end of test, heritability estimates (h 2 ) (6s.e.) were 0.18 (60.11) for total WBC count. For PBML subset proportions, the heritabilities were 0.52 (60.14) for gd TCR 1 cells, 0.62 (60.14) for CD4 1 cells, 0.44 (60.14) for CD11R1 1 cells, 0.58 (60.14) for B cells and 0.59 (60.14) for monocytes. Farm health status affected the heritabilities for WBC, being substantially higher on lower health status farms, but did not have consistent effects on heritabilities for the PBML subsets. There were significant negative genetic correlations between numbers and proportions of various PBML subsets and performance, at both start and end of test. In particular, the proportion of PBML cells that were CD11R1 1 cells, at end of test, was strongly correlated with daily gain (r g 5 20.72; P , 0.01). There were also weaker but significant negative phenotypic correlations between PBML subsets measured at end of test and performance, for gd 1 T cells, CD8a 1 , CD11R1 1 cells, B cells or monocytes. Phenotypic correlations with daily gain were generally lower at the start of test than at the end of test. These results show that most of the major pig PBML subsets are heritable, and that systemic levels of several of these PBML subsets are genetically negatively correlated with performance. This approach provides a basis for using immune trait markers when selecting boars that can produce higher-performing progeny.

Traits associated with innate and adaptive immunity in pigs: heritability and associations with performance under different health status conditions

“…Previous work by ourselves and others, has demonstrated negative phenotypic and genetic relationships between some immune traits and weight gain [4,13,14,35]. This study confirms and extends these earlier findings.…”

On the Genetic Interpretation of Disease Data

“…This is best illustrated from extensive datasets collected in farmed livestock. For example, components of innate and adaptive immunity are often moderately to highly heritable in commercial pig populations [14], [15], whereas the heritability of observable disease in such animals is low to moderate at best [16], [17]. Whilst true presence or absence of disease, given exposure to infection, will be largely a function of the immune response, we have demonstrated that the actual prevalence of disease and the estimable genetic variation between animals will be influenced by variable exposure and the sensitivity of diagnosis.…”

Selection of pigs for improved coping with health and environmental challenges: breeding for resistance or tolerance?

“…Genotype by PRRS infection level interaction for reproductive traits was demonstrated by Lewis et al (2009). Additional information about potential genotype by health status interactions has been reported by Clapperton et al (2008) and Clapperton et al (2009), who found different heritability estimates for pig herds with different health status for some immune traits. Heritabilities were higher in high health status for CD4+ and CD11R1+ cells in both studies.…”

“…An indirect indicator for disease incidence or animal health status is measurement of immune responsiveness. Immunological traits have been found to be associated with performance (Clapperton et al, 2008, 2009). Immunological traits have also been found to display genetic variation, within and between breeds (Henryon et al, 2006; Clapperton et al, 2009; Flori et al, 2011), demonstrating the possibility of breeding for resistance, tolerance, or both, through selection of an immune response.…”