Any pollster will tell you that their predictions - especially around certain presidential elections - are fraught with peril. Fortunately, the predictions employed by researchers to select for disease resilient pigs have the potential to be far more accurate. As part of the push for greater accuracy, scientists are experimenting with a variety of tools such as the CBC (complete blood count) test.
“High health status in nucleus and multiplication farms at the top of the swine breeding pyramid is a barrier to genetic selection of disease resilient pigs,” said Jiehan Lim, MSc student in the Faculty of Agricultural, Life & Environmental Sciences at the University of Alberta. “This resulted in a gap between the performance measured in the breeding company and the performance observed at the commercial level.”
Success is in the blood
To address this gap, researchers evaluated a test commonly used in both human and veterinary medicine to gauge general health. This involved identifying key differences in the complete blood count between resilient and susceptible animals before and after a natural disease challenge, and assessing the potential of CBC as a tool for breeders to select disease resilient animals in a high health environment.
“We studied 893 high health crossbred barrows from multiplication farms. These barrows were introduced in batches and exposed naturally to multiple diseases simultaneously in a test station. Natural disease challenge was established using seeder pigs to simulate high disease pressure typical of a commercial situation. Performance traits (growth rate and treatment rate) were assessed and used to classify pigs into resilient and susceptible groups.”
Using the CBC test, Lim and his colleagues profiled 29 disease-related parameters on blood samples collected from individual pigs prior to and following the disease challenge. Most significantly, in contrast to resilient pigs, susceptible pigs were found to have a low neutrophil concentration before challenge and a persistently higher concentration of neutrophils when the challenge was complete.
For non-scientists, this finding may prompt two poignant questions: What are the implications for industry, and what the heck is a neutrophil?
Addressing the second question first, a neutrophil is a type of immune cell that is one of the first cell types to travel to the site of an infection. As for the implications, the test results provide evidence that pre-challenge CBC could potentially be used by breeders in the classification of resilient and susceptible pigs in genetic nucleus and multiplication farms with high health status.
“It appears that the CBC test could be implemented quite easily. If it proves reliable, it may support producers in precision livestock farming. For example, they could use less medication with resilient animals and more vaccinations for susceptible pigs.”
As far as they’ve come in studying and selecting for disease resilience, Lim is equally enthused about where they go from here.
“In trying different methods of prediction, we’ve managed to reach 60 per cent accuracy, but I think there is still room for improvement by using more animals and larger studies in our analysis. The idea of using tests like the CBC that are employed in human medicine to detect conditions like heart disease, anemia, infections and cancer, is intriguing."
It may sound like a stretch, but if pigs and humans can share heart valves, they should be able to benefit from the same blood test without missing a beat.