Breeding disease resilient pigs

Abstract

Animal breeding continues to play a role in improving the stability of farming systems by selecting resilient animals and developing methods of selection for disease resilience, disease resistance and disease tolerance. Routine veterinary observations on clinical and sub-clinical diseases as well as growth in challenging environmental conditions may be used as measures of disease resilience. However, disease resilience can only be measured reliably when a sufficient infection challenge is present in the standard farming system. Deliberately exposing a large number of animals to high infection levels to obtain more accurate measures of their disease resilience is not feasible due to welfare concerns and reduced profitability. Improvement in disease resistance and disease tolerance will lead to superior disease resilience. However, within- host infection levels have to be known for a reliable distinction between disease resistance and disease tolerance and this information is not expected to be available for farm animals. Genetic variation has been identified for direct measures of disease resistance, i.e. pathogen load, and indicators of disease resistance, i.e. susceptibility to disease and immune parameters. Selection strategies for direct measures of disease resistance (pathogen load) with beneficial health and welfare consequences for groups of animals lead to more robust environments that have lower levels of disease-causing organism and are less challenging for animals. Selection strategies for disease resistance with these consequences should be implemented in breeding programs. Multiple parameters including mean growth, mean pathogen load or mean of certain immune traits for groups of pigs as well as information on variation in air quality or heat load could be used to quantify the general infection challenge better. Variation in some of these environmental measures has already been observed in pig farms with good health and management procedures indicating that it is possible to select for disease resilience in commercial pig breeding programs.