Small litter sizes can be disappointing and have a real impact on your finances when you’re trying to make your pigs pay their way. Liz Shankland has some advice
Watching your first litter being born must rank as one of the highlights of being a pig keeper. But what if your sow appears to have a normal pregnancy and a trouble-free farrowing, but only produces a few piglets? I often get emails from baffled smallholders who just can’t understand why their sow or gilt, which looked the picture of health while pregnant and looked like her belly contained at least a dozen piglets, has ended up with as few as three healthy ones.
Successful breeding depends on a huge range of factors, including genetics, nutrition, environmental conditions, and, of course, disease. Some things you can’t control – but the one thing you can do is make sure that your pigs are fit, healthy, and vaccinated against some of the most serious diseases before you embark on breeding.
We often assume that a pig carrying a disease will show some physical symptoms, but that is not always the case; often, some diseases which can have a devastating impact on the viability of a litter – and so on the number of piglets which survive – are only suspected when things go wrong at farrowing time.
Protecting your stock against two major diseases which can cause reproductive problems – Erysipelas and Porcine Parvovirus (PPV) is a sensible first step. Both can be introduced into the herd when you buy in new animals, bring in a hire boar, or take your pigs to shows. Fortunately, it is possible to vaccinate to keep both diseases at bay (see panel).
What is Erysipelas?
Erysipelas is an infectious disease which has a serious detrimental effect on reproductive ability in sows and boars, as well as lameness, arthritis, heart disease, and even death. All ages of pigs can be affected.
The bacterium which causes the disease – Erysipelothrix rhusiopathiae – is easily passed from pig to pig. It has been estimated that up to 50% of all healthy pigs are carriers; the bacterium lives in the tonsils and is transmitted through saliva, faeces, or urine. It can live outside the pig for several months, surviving in faeces and in the soil, as well as in contaminated feed, bedding, and water. Stress or viral infections can often make a pig more susceptible. Birds can carry it, so poultry can be affected, as can sheep. If it is discovered at the abattoir, carcasses can be condemned.
What does it do?
The effects vary according to the age of the pig and the stage of pregnancy, but symptoms can include:
u Abortion and pregnancy failure
u Variable litter sizes
u High numbers of stillborn piglets
u Mummified piglets
u Infertility in boars
u Severe and recurring lameness
u Sudden death
In the acute form of the disease, the organism gets into the blood stream and causes a septicaemia, resulting in fever, stiffness whilst walking, or a reluctance to get up. In severe cases, the disease spreads so fast that a pig which previously showed no signs of ill-health will simply be found dead. As the organism multiplies in the blood stream, it blocks the blood vessels, causing raised, diamond-shaped or oval blotches which can be pink, dark red, or purple (see picture).
Sometimes infection does not cause obvious health problems, and the condition can remain undiagnosed or be mistakenly blamed on other factors. The pig may go off its food, be infertile, have failed pregnancies, and its temperature may be 39 to 40C. In the chronic form of the disease, arthritis develops in the joints and infection of the heart valves can cause heart failure. Erysipelas can be effectively treated with penicillin, if diagnosed in time, but vaccination against it is a much more sensible course of action.
Porcine Parvovirus (PPV)
Porcine Parvovirus is an infectious disease that kills developing piglets in the uterus of the sow or gilt, and is thought to be the most common and most significant cause of reproductive failure. The disease is thought to be present in more than 90% of herds in the UK but it can work away without the pig showing any clinical signs. It is transmitted through the nose or mouth, passes into the intestine, and is shed in faeces. Within three weeks of infection, it crosses the placenta and attacks the developing embryos and foetuses.
The results depend on the stage of pregnancy:
Gilts (females which have not yet had a litter) are the most susceptible to PPV around four or five months old, when the antibodies passed on by their mothers start to decline. Gilts should ideally be vaccinated at five months old, and always before being put to the boar for the first time. Sows develop immunity either by vaccination or through physical exposure to the virus, but there can be exceptions, so some vets will recommend not just an initial vaccination, but also an annual booster. Boars, too, need to be vaccinated. Although PPV does not have a detrimental effect on semen quality, boars can still transmit the virus via semen to sows and gilts.
Liz Shankland is the author of the Haynes Pig Manual and owns the Tudful Herd of pedigree Tamworth pigs. You can contact her through her website, www.biggingerpigs.com
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