Animals differ genetically not only in resistance to infections, but also in their ability to maintain their performance in the presence of an infection, i.e. tolerance to infections. This is the result from the study of Hamed Rashidi, PhD candidate at the Animal Breeding and Genetics Centre. On Friday 18 March, Hamed Rashidi will defend his PhD-thesis ‘Breeding against infectious diseases in animals’ at Wageningen University. Results from his study can be exploited in breeding programs to breed more resilient animals.
In his research, genetic analyses were done on virus infections caused by Porcine Reproductive and Respiratory Syndrome (PRRS) in pigs and nematode infections in sheep. Three types of response to infections were studied: resistance, which is the ability to control or reduce the amount of pathogen in the body, tolerance, which is the performance of an animal given the amount of pathogen (pathogen burden) and resilience, which is the combination of tolerance and resistance when there is no measure of pathogen burden per animal.
In pigs, he found that sows differ in their response to disease outbreaks of PRRS. PRRS significantly reduces the number of piglets born alive and the incidence of abortion. Some sows had large reductions in total number of piglets born alive or even an abortion, while others had much smaller reductions in total number of piglets born alive. In another part of his study, genomic regions were detected related to tolerance when investigating growth rate of finisher pigs infected experimentally with PRRS. He found in sheep a strong trade-off between resistance and tolerance indicating that animals are genetically good in either resistance or tolerance, but usually not in both. In a simulation study, it was found that breeding to increase resilience in absence of records on pathogen burden is a pragmatic approach to increase both resistance and tolerance to infections. These results show good opportunities for livestock breeding programs to breed animals that are more resilient to diseases.
The research was done in collaboration with Topigs Norsvin BV, the University of Glasgow, the University of Edinburgh and the PRRS Host Genetics Consortium led by Iowa State University. This research was part of the NematodeSystemHealth project, financed by Marie Curie Initial Training Networks (FP7-People-2010-ITN), and co-financed by Topigs Norsvin, The Netherlands, and Dutch Ministry of Economic Affairs, Agriculture, and Innovation (Public-private partnership “Breed4Food” code KB-12-006.03-004-ASG-LR and KB-12-006.03-005-ASG-LR).