Background and history

This condition is becoming more common in modern pig producing systems particularly in the first litter gilt where the skeleton is still growing and there are heavy demands on calcium for milk production which result in demineralisation of bone..

Bones affected with OP are quite normal in their structure but they become thinner particularly in the dense parts and shafts of the long bones. As a result they become more prone to fracture. OP can arise due to a shortage of calcium in the diet and imbalance of calcium and phosphorus, poor or inadequate absorption from the diet, with heavy losses during lactation and where there is a lack of exercise.

Clinical signs

Sows

• Pigs show pain / discomfort.
• Sudden lameness
• Fracture of long bones.

Piglets, weaners and growers

• Rare

Diagnosis

This is based on clinical signs, a history in lactating and newly weaned sows and evidence of fractures of the long bones. If the herd has a problem it is necessary to examine the bones of an affected animal by x-ray to differentiate between OP and OM. Calcium and phosphorus levels may be normal.

Similar diseases include:

• Leg weakness or osteochondrosis.
• Spinal fractures.
• Torn muscles at their insertions into the bones.
• Mycoplasma hyosynoviae infection.

Causes

• Loss of calcium and phosphorous during lactation.
• Faulty nutrition.
• Age of pig.

Prevention

• Outbreaks are often more apparent in new gilt herds. Selection of animals for good conformation is essential.
• Investigate the growth rates and nutrition and feeding in the gilt.
• Increase exercise during pregnancy if possible.
• Check the levels of calcium and phosphorus in the diet. They should be 10-12g/kg of calcium and 8-10g/kg of phosphorus.
• Only mate gilts from 220 days onwards and if the disease is a persistent problem in a particular genotype change the source.
• Check that floor surfaces are not slippery.
• The problem is less common in outdoor herds.
• Feed a good lactation diet during suckling and consider top dressing the diet daily with 20g of di calcium bone phosphate.
• Inject pregnant animals with 50,000iu vitamin D3 three weeks prior to farrowing. Repeat again in the second week after farrowing.
• Maximise feed intake to appetite during lactation.
• Check the ratio of calcium : phosphorus in bone ash. The normal ratio is approximately 2:1 or less. In problem sows this is often 3:1 or more

Treatment

In cases of bone fracture the pig is best destroyed on humane grounds.