Background and history

Osteomalacia is a condition responsible for the downer sow syndrome. Fractures of the long bones at the mid shaft and fractures of the lumber vertebrae are common, with the sow becoming paraplegic. The condition is due to inadequate levels of calcium, phosphorous and vitamin D in the ration. Sometimes sows cannot absorb sufficient micro-nutrients in spite of there being adequate levels in the diet. OM is also associated with immature skeletons, an imbalance of calcium and phosphorus and vitamin D and/or a failure of the sow to consume adequate feed and satisfy her nutritional requirements. Large amounts of calcium and phosphorus are excreted into milk from the bones resulting in weaker less dense bone which predisposes to fractures. Bone mass is also lost due to lack of exercise during confinement in the farrowing crate.

Clinical signs

Sows

• Seen in the first litter gilt.
• Dog sitting position.
• Stiffness
• Sudden acute lameness during lactation or immediately post weaning.
• Fractures.
• Pigs show pain / discomfort.

Piglets

• N/A

Weaners and growers

• Stiffness.
• Lameness.
• High incidence of fractures of he main bones at slaughter.

Diagnosis

This is by the clinical signs. Similar diseases include:

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

Causes

• Inadequate diet.
• Heavy milk production.
• Low feed intake in lactation.
• Breed of animal.
• Shortage of vitamin D3.
• Low calcium in the diet.

Prevention

Once OM has developed treatment is of minimal effect although injections of calcium phosphorus and vitamin D may help. If your herd has a problem consider the following:

• Feed a high dense diet in lactation 14.5MJ DE/kg and18% protein.
• Check the levels of calcium and phosphorus (minimum 0.9% and 0.75%). In first litter animals it may be necessary to raise the levels to 1.2% and 1%.
• Give up to 100,000iu vitamin D3 by injection 10 days before farrowing.
• Keep gilt litters to ten piglets or less.
• Top-dress the feed in lactation with calcium/phosphorus.
• Bone ratios of calcium/phosphorus in affected sows are often 3:1 (normal < 2:1).
• Mate gilts younger 210 to 220 days.
• Use a good lactation diet and feed through to 21 days post-mating.
• Provide non slip floors in farrowing crates.
• Wean first litter females singly and use a light weight boar.
• Provide exercise to the pregnant gilt.
• Check parasite levels to ensure no dietary insufficiencies arise.

Treatment

• In the early stages move the sow to well bedded loose housing.
• If there are no fractures inject with calcium and vitamin D3
• If there is a problem in first litter females inject them with vitamin D3 after farrowing and 7 days later.
• Supplement the diet with dicalcium bone phosphate 30g day of sterilised bone flour.
• If there are fractured bones affected sows should be culled or destroyed.