Rearrangement of genetic material in pigs causes economic loss for producers
By Kate Ayers
Researchers are helping to reduce the prevalence of chromosome rearrangements in the Canadian swine population through screening.
Rearrangement of the genetic material in chromosomes is a major cause of reproductive dysfunction in pigs and can result in early embryonic mortality, Brendan Donaldson, a PhD student in the department of biomedical sciences at the University of Guelph, explained during its Swine Research Day last week.
Chromosomes can become mismatched, containing DNA from two or more chromosomes. This phenomenon occurs in about one in 100 piglets.
Animals who are carriers of rearranged chromosomes may appear normal, but they can create unviable sperm or egg cells, Donaldson’s study said. This misalignment of chromosomes during meiosis can lead to embryonic loss.
Of the 13 million pigs in Canada, 1 to 2 per cent of these animals have a chromosome abnormality that affects their ability to reproduce, Dr. Allan King, a professor at the University of Guelph, said to Farms.com on Thursday.
The heritability of this chromosome rearrangement trait and resulting smaller litter sizes can cost producers quite a bit of money, he added.
Indeed, this trait is highly heritable and is present in all major breeds. Carriers generally experience a 25 to 50 per cent decline in fertility and pass chromosome rearrangement to 50 per cent of their surviving offspring. As a result, rearrangement can spread throughout the population, the study said.
Due to the implications of this trait on the swine industry, the King Lab at the University of Guelph began the largest swine cytogenetic screening operation in North America. The initiative has screened over 3,700 boars since January 2015.
The cost of cytogenetic screening for each boar is $175. “However, the cost benefit of 5.3 makes testing worth while,” King said. This ratio translates to a $5 return for every $1 invested.
The process is labour intensive, so producers can expect to receive results three to four weeks after the initial screening.
Producers who screen their breeding boars can remove animals from the herd if they have the chromosomal rearrangement trait.
Since the lab began screening over successive generations, researchers have seen a significant reduction in the number of rearrangements by the fourth generation, the study said.
That said, the scientists have found a rise in mosaic (single cell) chromosome rearrangements in the population.
Future research will observe the genetic material of rearrangement carriers to better understand rearrangements and identify the genomic factors behind their formation, the study said.
Chromosomal screening, which facilitates the removal of carriers from swine populations, is currently the only method to detect the rearrangement trait in pigs.
In addition to Donaldson and Dr. King, Daniel A.F. Villagomez, Tamas Revay and Samira Rezaei contributed to this study.
If producers are interested in learning more about the screening process offered by the Karyotekk laboratory at the University of Guelph, more information is available on the lab’s website. Inquiries can also be directed to firstname.lastname@example.org.
Updated May 26, 2018