Blood test can identify litter-limiting genetic problem in pigs


A lab has been established in Guelph to screen boars with a genetic abnormality that results in smaller litters.

The abnormality happens naturally, when cells divide.

“Sometimes, the genes just don’t line up the way they should when cells are developing,” says University of Guelph Prof. Allan King, who established the lab. That results in an abnormality called a chromosome translocation, which renders 3-4 fewer piglets per litter than normal.

In developed countries, that translates to about a $100 loss per litter.

Boars affected by the abnormality show no outward signs of problems, making it easy to miss. As a result, the condition is passed on through generations. About one-half of the offspring of an affected boar will have the same trait.

King says the abnormality happens in about two per cent of all pigs. Considering there are 13 million pigs in Canada, and about one billion in the world, the numbers of pigs affected by this problem are huge.

King, who holds the Canada Research Chair in Animal Reproductive Biotechnology at Guelph, started this research 40 years ago, as a graduate student in Sweden.

Through his studies and subsequent research by his students, it was determined the problem is a natural phenomenon that in pigs affects litter size.

In living organisms, DNA constantly breaks during cell development. When this happens, cells try to “glue” the two broken pieces back together.

Usually, this process goes smoothly, even though there are millions of pieces of DNA floating around inside a cell.

But sometimes, for reasons unknown, the wrong two pieces come together. “Maybe it’s a side effect of DNA being able to change, we don’t know,” says King. “We’re trying to find some genetic markers that will give us more clues.”

Whatever the reason, this abnormality in pigs results in some embryos not developing full term.

The blood test to identify boars with the abnormality is carried out at the Ontario Veterinary College, in conjunction with Guelph’s Animal Health Laboratory. It’s one of a half-dozen labs worldwide testing for chromosome translocation, and the only one in Canada.

Since 2014, researchers and technicians at Guelph have tested over 3,000 boars.

The test is effective, but it’s also labour intensive and relatively expensive at $175 per sample. Working through the university’s business development arm called the Catalyst Centre, King and his colleagues Daniel Villagomez and Tamas Revay are trying to make it more efficient through automated blood sample scanning.

But even at the current cost, King says identifying just one problem boar in a producer’s herd pays for the cost of the test, given how the condition can spread with one boar servicing multiple sows.

The lab was established with support from the Ontario Ministry of Agriculture, Food and Rural Affairs, the Canada Research Chairs’ program and Guelph’s Department of Biomedical Sciences.

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