Depopulation
Why Depopulate?
- compulsory slaughter due to a notifiable disease.
- chronic low productivity or high production costs.
- high medication costs.
- specific non-notifiable infectious disease.
- to allow for building refurbishment or major changes to the system.
The result of depopulating/repopulating - healthy, high performing pigs
Methods of Depopulating
Traditional Method
The traditional method of depopulating a breeding herd is to stop serving allow the growing pigs to work their way through the system; the repopulation then takes place after a cleaning and resting period with maiden gilts that are grown on to serve subsequently farrowing and filling the feeding herd.
In practice this means that for a farm producing bacon pigs and leaving the farm empty of pigs for 8 weeks no pigs are sold for more than a year.
Method for Reducing Downtime
The amount of downtime can be reduced by using three different sites during depopulation/repopulation.
Site 1 - Growing site - pigs from the old herd are moved onto this site; the younger the feeding pigs can be moved to this site the better.
Site 2 - Main Farm - this can be cleaned and disinfected whilst sales are continuing.
Site 3 - Breeding Site - gilts can be served on this site and then moved to the main farm once the cleaning and resting are complete.
Operating three sites has the potential to reduce the loss of sales to 10 weeks.
Cleaning Procedure
- Remove all solid and liquid manure.
- Powerwash all surfaces including slurry channels, ceilings and fan housings.
- Empty and clean midden areas.
- Disinfect all areas twice. The cleaning of some buildings e.g. dry sow accommodation can be done initially whilst the herd is depopulating but the second disinfection should be delayed until the last pig has left the farm.
- Finally fumigate or lime wash solid surfaces.
Resting
- The period of time which the site must be left empty of pigs will be determined by practical considerations and the diseases present. A minimum of 6 weeks is required but if e.g. Swine Dysentery is present this would need to be extended to 8 weeks.
- During the resting period it is essential to carry out a vigorous campaign of vermin control.
- An essential element of the depopulation/repopulation programme is to review Farm Security. This is required so that the clean herd is protected against the re-introduction of disease.
Summary of paper presented by Mark White at the Northern Ireland Pig Discussion Group Conference, March 1998.
