Reduce disease risk
Many pork producers have suffered severe financial loss because of diseases introduced from other piggeries. Moving pigs is the most common way to spread disease. Other carriers such as people, vehicles, rodents and dogs may also introduce disease into the piggery environment. For information specific to your herd, consult a veterinarian.
Some producers keep a closed herd and do not introduce other pigs into the unit. If new genetic stock must be introduced, the safest way is by artificial insemination (AI), after appropriate health tests on the donor boars.
An option is to buy boars and keep them away from the main piggery and use them in an on-farm AI program. Another option is to hold pregnant sows away from the main herd and hysterectomy or hysterotomy (Caesarian) them. These techniques are not only applicable to specific pathogen-free (SPF) piggeries.
If for some reason AI is not feasible and live pig introductions are necessary, buy them from a reputable breeder or breeding company, and preferably only from herds of high health status (SPF). When starting a new piggery, serious consideration should be given to purchasing foundation stock from a herd with a high health status (SPF herd). Consult your veterinarian to match the disease status between herds. All introduced breeding animals should come from herds free of brucellosis. Ideally pigs should be introduced from one source.
Each pig carries a range of bacteria and viruses which it is immune to but which can cause disease in pigs reared elsewhere. The greater the number of introductions made, the greater the chance of introducing disease.
Limit the number of live animal introductions to boar replacements. If purchasing female pigs, it is preferable to purchase maiden gilts than pregnant sows. They should be vaccinated and/or treated before introduction and tested before purchase.
Buying at saleyards
Buying pigs from unknown sources at a saleyard is not recommended as it is the surest way to introduce disease especially swine dysentery. Pigs transported to a saleyard, penned and then moved to another piggery are subjected to considerable stress. This may cause the onset of disease, for example, scouring or pneumonia. They may also pick up harmful bacteria from other pigs and although healthy when purchased, become sick later.
If it is necessary, only healthy-looking pigs should be considered and they should come from a small number of piggeries whose health status is known.
It is strongly recommended that weaners or stores be purchased on the property of origin and taken direct to their destination.
Ideally, prospective purchasers should employ a veterinarian to undertake an exhaustive and thorough check of prospective herds to guard against the introduction of disease. This may be expensive and appear unrealistic under some circumstances, but it is important to remember that introducing a new disease to a herd is very expensive.
A veterinarian who regularly attends to a vendor's herd can be asked to certify its health monitoring and the disease status of the herd.
Herd health monitoring includes examining pigs at slaughter. Having a veterinarian carry out this check assists in disease-matching a herd against other herds so that the producer can purchase replacement breeding stock from herds of similar health status. It also enables the development of disease control/treatment strategies for pigs that are introduced into a herd.
Serological tests are available for the diagnosis of Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae.
SPF herds should be free of enzootic pneumonia, swine dysentery, porcine pleuropneumonia, swine brucellosis, internal and external parasites, but prospective buyers should not assume these diseases are absent as disease breakouts occur. A tighter disease security system should be adopted in units with high health status.
All new stock should be quarantined in suitable accommodation at least 100 m (500 m is better, 2-plus km is better still and for large numbers 3 km is advisable) away from the herd for a period of at least 30 days (may be 60 or greater days).*
After two to four weeks, expose some home-produced finisher pigs destined for slaughter to the introduced pigs for a period of at least one month during the quarantine period to check for the development of disease.
There should be no medication (antibiotics or growth promotants) in their feed of the home or introduced pigs in the quarantine area (e.g. for the first two weeks) to suppress potential diseases and all pigs should be closely observed for signs of disease.
The quarantine period serves three purposes:
- it allows any disease the animals may be carrying to incubate and develop
- it exposes the homebred slaughter pigs to diseases carried by the introduced animals
- it allows the introduced animals time to build up immunity against germs on the property (e.g. all piggeries have different E. coli populations to which new stock should be gradually exposed. In this way they build up their immunity slowly but more effectively than by being suddenly exposed to large numbers of hostile microbes).
Consult a veterinarian when quarantined animals appear sick. Ideally, a person having no contact with the main herd should tend the quarantined pigs. Where this is not possible, their needs should be attended to after those of the main herd. Separate equipment should be used and protective clothing should be worn. In SPF herds a complete change of clothing plus a shower is necessary.
Rodents carry and transmit diseases, such as swine dysentery, leptospirosis, salmonellosis and some viral diseases, therefore ensure rodents are controlled.
The veterinarian can advise whether the new pigs can enter the herd. Some producers also have in-contact animals examined at slaughter for signs of introduced disease. If all pigs are healthy after one month (ideally two or possibly more)* of isolation, the new pigs can join the herd with a reduced risk of introducing disease. If unsure about the new pigs' vaccination and medication history, vaccinate and/or treat them before introducing them to the herd proper.
Even when these guidelines are followed there is still a possibility that a live pig may introduce a disease.
* The distances and times may need to be greater, depending on which diseases your herd is free, and how the process is managed. Talk to your veterinarian.
Other measures to assist in reducing the introduction of diseases into a piggery include:
- erecting perimeter fencing around the piggery area
- minimising visitors
- requiring visitors to be pig-free for 12 hours and providing them with farm boots and clothes
- being aware of the risks associated with being near other pigs and animals and carrying dung, saliva, mucus on clothes
- requiring trucks to be pig-clean and restricting access to drivers
- providing a loading ramp at least 20 m away from the piggery clean area (an option for small herds is to use a farm truck to take the pigs to a carrier's vehicle)
- disinfecting equipment used on other piggeries
- practising good hygiene to control vermin.
Every piggery owner needs to decide on a disease security level and stick to it. A suggested security format for a 50-sow or more commercial piggery is:
- Consider using AI for genetic improvement. Introduce new stock as seldom as possible and buy only from sources with a high health status. Quarantine introduced stock with a few home-produced pigs for one or two months at least 100 m from the rest of the herd. Check the health status of all pigs in quarantine.
- Erect signs clearly stating 'No unauthorised entry'.
- Provide boots and overalls for visitors and keep visitor numbers to a minimum.
- Do not allow vehicles that visit other piggeries or carry other pigs closer than 50 m to the piggery.
- Keep rodents under control and deny piggery access to feral pigs and other wandering livestock.