A Methodology to Quantify Resilience in Growing Pigs

Abstract

There is a growing concern about the genetic determinism of resilience and its possible implementation in breeding programs. The objective of our study was to elaborate novel resilience indicators in growing pigs based on the deviation from the expected growth curve and the increment of the acute-phase protein haptoglobin (HP) after applying a common vaccine. A total of 445 pigs were vaccinated with an attenuated Aujeszky vaccine at 12 weeks of age. Deviation from the expected body weight (ΔBW) given the growth curve of unvaccinated pigs at 28 days post-vaccination (DPV) and the increment of HP at 4 DPV (ΔHP) were suggested as resilience indicators. Challenged pigs that maintained their productivity and had a minor activation of HP were deemed resilient, whereas pigs that had low ∆BW values and a high activation of HP were deemed susceptible. Pigs were also classified based on ∆BW and ∆HP relative to the expected BW at 28 DPV and to the basal level of HP, respectively. The concordance was high between both methods, indicating that ΔBW and ΔHP are not sensitive to the animal's expected BW nor the basal level of HP. The heritability estimates were moderate for ∆BW (0.33) and low-to-moderate for ∆HP (0.16). Our study suggests ΔBW and ΔHP as novel resilience indicators in pigs. The suggested indicators capture different aspects of resilience, are easy to measure, and are genetically controlled. Thus, they may be improved through selective breeding. Further analyses are needed to validate our findings.

Keywords: body weight; haptoglobin; pigs; resilience indicators; vaccine challenge.

Figure 1

Timeline and experimental design.

Figure 2

Classification of pigs as resilient, average, and susceptible based on the first (Q₁) and the third (Q₃) quartiles of ∆BW and ∆HP. ∆BW: body weight deviation from the expected growth curve of control pigs at 28 days post-vaccination, ∆HP: haptoglobin increment at 4 days post-vaccination.

Figure 3

Projection of the resilient, average, and susceptible groups obtained with the first (Q₁) and third (Q₃) quartiles of ∆BW and ∆HP on the plane defined by %HP and %BW. Individuals were colored according to their group classification using the criterion from Figure 2 to visualize concordance between both methods. ∆BW: body weight deviation from the expected growth curve of control pigs at 28 days post-vaccination (DPV), ∆HP: haptoglobin increment at 4 DPV, %BW: ratio between ∆BW and the expected body weight at 28 DPV, %HP: ratio between ∆HP and the basal level of haptoglobin.

Figure 4

Growth curves of pigs from the resilient and susceptible groups. The grey band represents the confidence interval. Individuals were colored according to their group classification using the criterion from Figure 2.