BREEDING & GENETICS ▶▶▶
Breeding for robustness as the way forward
Breeding strategies can be used to improve pig health. The method is to select individuals with improved response to a specific pathogen challenge – or animals with improved response to a number of diseases. This approach is known as “breeding for robustness”. What does that entail?
BY VINCENT TER BEEK, EDITOR, PIG PROGRESS T
hriving despite a tough (pathogen) challenge; that sums up pretty well the benefits of the breeding strategy revolving around robustness. Dr Jenelle Dunkelberger, Topigs Norsvin’s geneticist for the
United States, is on top of this concept’s development.
Pig Progress: What does robustness actually mean? Dr Jenelle Dunkelberger: “Robustness refers to the ability of an animal to maintain performance following exposure to disease. From a practical standpoint, sometimes you see pigs that, despite being exposed to disease, are able to cope with that challenge and maintain a high level of performance. We would call that a very robust animal. “On the other hand, we also see pigs that, following expo- sure, develop clinical signs and symptoms of infection, fail to thrive and, in the most extreme cases, die. That’s an example of a particularly non-robust animal. “Our goal is to improve robustness to disease – to have more animals that may or may not become infected but, regardless, are able to maintain performance despite a pathogen challenge.”
How can robustness be bred for? “Our approach is to use traditional breeding strategies to enhance robustness to disease. This is the same technique that we use to improve all of the other economically impor- tant traits in our breeding goal. It’s using phenotypes and genotypes to calculate breeding values that can be used to make mating decisions and produce progeny with enhanced performance under challenge. Following a disease challenge, we see evidence of naturally occurring variation in how animals respond to the challenge. When we quantify that
22 ▶ PIG PROGRESS | Volume 37, No. 1, 2021
variation, we see that a substantial proportion of the pheno- typic variation is due to genetics. From this perspective, using traditional breeding strategies to breed pigs with enhanced robustness to disease is very feasible.”
How does robustness work in practice? “The basic definition of robustness is being able to maintain performance following exposure to a pathogen. There are dif- ferent reasons why an animal might be capable of doing that. One is that the animal is more resistant to the disease, and the other is that it is more tolerant to the disease. “Resistance refers to the ability of the animal to somehow block or suppress the lifecycle of the pathogen. A pig might be more resistant because it is able to block that pathogen from entering and infecting the host cells; that is one possi- bility. Or it can limit the replication of that pathogen once it is infected. “Tolerance refers to the ability of that animal to maintain per- formance despite pathogen level. So if an animal is complete- ly tolerant, it doesn’t matter how much virus it is infected with – it is able to maintain the same level of performance.”
Will the sophisticated technology available today al- low you to dive a lot deeper into the data and make more educated choices? “Exactly. We can identify individual genes or subsets of genes that are associated with superior performance during a challenge.”
Why do you consider breeding for robustness to be sustainable? “Robust animals, by definition, are less affected by a disease challenge and therefore require fewer antibiotics. For many of the large producers in the US, decreasing antibiotic usage is part of their long-term strategy to enhance sustainability. Breeding pigs for enhanced overall robustness to disease is also a good insurance policy. Using this approach, we are breeding pigs that will perform well not only in the face of current disease challenges, but to future disease challenges too. “So, how can we produce pigs with enhanced robustness to disease? There are two main approaches – traditional breed- ing and gene editing. Traditional breeding is the process we already use to improve the traits in our breeding goal. It’s well
PHOTO: TOPIGS NORSVIN | MAARTJE VAN BERKEL
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