Not specific to any breed, line or genetics provider, RTs fortunately are a rare occurrence – about one in 150 boars inherit this trait and in about one in 5,000 boars it shows up de novo (spontaneously developed, not inherited.)

A boar with a RT can cause:

• Formation of ‘unbalanced’ sperm cells, and ultimately embryos, resulting in early embryonic mortality (see Figure 1 below)
• Farrowing rates are near normal (sperm still fertilize, but embryos may die)
• Litter size consistently reduced up to 50 per cent
• Half of live born offspring will carry the rearrangement, promoting its distribution

Figure 1. The formation of normal, lethal and viable (survive to pass on the RT) sperm cells.

The calculated potential impact of a boar with a RT is significant over the stud life of a boar – an estimated $84,240. (See chart below.)

“We need to emphasize that RTs are not specific to PIC or any genetics company, or to any line or breed for that matter,“ said Amanda Williams of PIC technical services. “But as a market leader, PIC has decided to take a leadership role in addressing and educating producers on this issue.“

PIC is providing testing (karyotyping) that is unique to North America via blood sampling of boars selected on performance test results. Testing is done only on sire lines, Williams added, because PIC selects for litter size in maternal lines, which in essence screens against this mutation by definition. As there were no commercial laboratories offering this testing in North America, PIC’s parent company (Genus) laboratory in DeForest, WI took the project on and successfully established a karyotyping facility using expert advice from Professor Darren Griffin at the University of Kent, UK. The technology was first applied to GN herd sires in 2009 and was ramped up this summer to screen all elite sire line boars.

CBVPlus and CBVMax boars screened

For many years, PIC has calculated a Crossbred Breeding Value (CBV) for their boars. This innovative system measures the performance of crossbred sibs sired by the same Genetic Nucleus (GN) sires, raised and managed in commercial environments. The system helps PIC more accurately select pure lines based on how progeny are expected to perform in actual commercial conditions, not the pristine GN environment required for biosecurity reasons.

“This approach ensures that customers receiving boars selected by this method access real-time commercial sib test data that translates to faster genetic improvement and performance advantages on their farms,“ Ms Williams said.

The CBVPlus and CBVMax categories features boars with the highest CBV value ranking of all PIC sires. CBVPlus and CBVMax boars are elite PIC AI sires, and as such we employ all possible technology to ensure against even the rare RT boar slipping through.

CBVPlus and CBVMax boars going into customer systems have been tested for RTs since July 2010. Before customer testing started, testing began on all new GN herd sire boars as of January 2010, following successful preliminary testing beginning in August 2009. Although not trivial, the cost of the test more than offsets the potential economic losses a boar with a RT will cause during their life in a commercial stud.

Testing is only available on PIC CBVPlus and CBVMax category boars.