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PMWS and the Benefits of Changing Breed

by 5m Editor
18 June 2007, at 12:00am

By Dr GrantWalling, and Stuart Cartwright, JSR Genetics. Many farms unfortunately now have practical experience of Postweaning multisystemicwasting syndrome (PMWS).

The effects on the cost of production are large due to the increased mortality of both the growing and finishing pig. The true impact of the disease further escalates due to decreased growth rates, increased FCR and the difficulties of managing larger numbers of sick animals.

Whilst a potentially successful vaccine may now be on the horizon, producers have had to adopt alternative measures to controlling the disease. One anecdotal method has been the change of terminal sire. This has led producers to try alternative terminal sire breeds such as Pietrain, Duroc and Hampshire. Interestingly the Danes have recently stopped using Hampshire terminal sire boars in the belief that it to be the cause of higher levels of mortality. Their programme is now purely based around the Duroc terminal sire.

At JSR we have investigated whether the anecdotal reports are scientifically robust by organising trials through standard commercial UK farms. This has involved detailed recording of over 2000 slaughter pigs through a farm that has PRRS, EP and PMWS. Results are summarised in Table 1 and the days to slaughter summarised in the Figure 1.

Large White
Sired Progeny
Titan (Pietrain)
Sired Progeny
Benefit to Titan
Number 902 1151
Pre-Weaning Mortality 13.4% 6.5% -51.3%
Post-Weaning Mortality 9.0% 4.4% -50.5%
Days to Slaughter 182 177 - 5 days
Table 1.


The results demonstrated a significant advantage (up to 6.8p/kg reduction in cost of production) and therefore a benefit of changing breed to the Titan sire line for farms with higher levels of disease challenge.

Those farms that do change their terminal sire should ensure that they fully research the effect on their business. Duroc terminal sires will produce more coloured progeny with deep seated hair but may allow access to higher meat eating quality markets. Hampshire progeny may also produce more coloured progeny and lower carcase yields and killing out percentage making them less desirable to the processors. Titan genetics may require producers to readdress their feeding rations during the growing and finishing phase on their farms, due to lower feed intakes but higher levels of feed efficiency (lower FCR).

Changing to an alternative terminal sire is therefore beneficial for many producers but only if properly researched and integrated into the business.

March 2007