Background and history

Next to reproductive failure, lameness is the second most common cause of sows being culled. Most cases occur from weaning through to the point of farrowing. A lameness problem increases the culling rate, reproductive problems and the non productive sow days so reducing the litters and pigs weaned per sow per year. Often problems involve first parity gilts or second parity sows, just as they are reaching the most productive part of their life. Sows culled for severe lameness may have to be shot on the farm because on welfare grounds they should not be transported. Therefore they contribute significantly to the recorded sow mortality. In order to analyse a lameness problem on a farm it is important to keep accurate records about each sow. These should include the following:

• Sow number.
• Parity.
• Breed and genetic line.
• Date of mating.
• Date of farrowing.
• Date of weaning.
• Date of lameness.
• Type of lameness.
• Housing area.

Alternatively you could use the farrowing rate loss sheet that is used in the dry period.

Clinical signs

Sows

• Pig off food.
• Sometimes fever.
• Reluctance to stand.
• Swollen joints / Fractures.
• Evidence of other diseases.
• Loss of balance.
• Arthritis.
• Dog sitting position.
• Not accept boar at mating.
• Pig shows pain / discomfort.

Piglets

• As for sows.
• Shivering.

Weaners and growers

• Pig may be off food.
• Sometimes fever.
• Reluctance to stand. Difficulty moving.
• Swollen joints / Fractures.
• Evidence of other diseases.

Causes

Infectious causes

• Brucellosis
• Clostridial diseases
• Erysipelas
• Foot-and-mouth disease
• Foot rot, Bush foot
• Glässers disease, (Haemophilus parasuis)
• Mycoplasma arthritis
• Salmonellosis
• Swine vesicular disease
• Streptococcal infections

Non infectious causes

• Fractures
• Laminitis
• Leg weakness (OCD)
• Muscle tearing
• Nutritional deficiencies
• Porcine stress syndrome
• Toxic conditions
• Trauma

In the maiden gilt or during the first pregnancy infectious lameness is usually due to erysipelas, glässers disease, mycoplasma infections and brucellosis in those countries where it is endemic. Clostridial diseases are rare in the dry sow but infections of the claws and hock areas due to trauma (foot rot and bush foot) are common causes. Foot-and-mouth disease and the vesicular diseases are discussed in chapter 12. In such infections a number of sows in both the dry sow area, the lactating area and indeed pigs across the unit will have varying degrees of lameness and blistering around the nose, mouth and feet. If there is a herd problem use the table below to help identify the cause.

Tissue changes that cause lameness

• Apophyseolysis (OCD) - Separation of the muscle mass from the growth plate on the pelvis.
• Arthritis - inflammation of one or more joint.
• Damage to nervous tissue - Clinical signs vary (e.g. partial or complete paralysis of one or more limbs) depending on the site of the damage.
• Epiphyseolysis (OCD) - Separation of the head of the femur.
• Fractured bones - Common in the hip, hock and elbow joints.
• Haematoma - Haemorrhage into the tissues.
• Laminitis - Inflammation of the tissues connecting the hoof to the bone. It is not common.
• Myositis - Inflammation of muscles.
• Penetrated sole - Damage due to trauma.
• Periostitis - Inflammation of the membrane (periosteum) which covers the bone.
• Osteitis - Inflammation of bone.
• Osteochondrosis (leg weakness) - Growth plate and joint cartilage degeneration.
• Osteomalacia - Softening of the bones due to calcium/phosphorus deficiency.
• Osteomyelitis - Inflammation of all bone tissue including the spongy centre and bone marrow.
• Osteoporosis - Week bones due to an imbalance of calcium and phosphorous in the diet.
• Split horn - Poor hoof quality. Overgrown claws.
• Torn ligaments or muscles - A common cause of lameness particularly where muscles are attached to bones.

Calcium and phosphorous

With modern dietary formulations actual deficiencies arising due to defective diet would be unusual. Problems however occur due to faulty storage, the incorrect application of the feed or interactions that reduce the availability to the pig. The latter can result from intestinal disease, metabolic failures or adverse interactions between nutrition, the pig, management and the environment.

Bone is a very strong and dynamic structure with minerals constantly being removed and replaced. The intestines control the rates of absorption both into the body and skeleton and these are necessary to maintain an equilibrium between demand and excretion. The ratio of calcium to phosphorus in the diet is also an important factor in this equation and this should not rise above 2:1, when it does the absorption of calcium may be impaired, likewise if the ratio drops below 1:1. The ideal is approximately 1.25:1 to 1.50:1. Vitamin D3 is also required in calcium metabolism together with controlling hormones produced by the parathyroid gland.

Osteodystophy

This is a general term to describe specific diseases that arise whenever there is a failure of bone structure and metabolism due to faulty nutrition. Such diseases include osteoporosis, rickets and osteomalacia, periostitis describing disease of the periosteum and osteomyelitis, disease of the centre or medullary cavity of the bone.

Osteochondrosis (degenerative leg weakness)

Degenerative changes in the joints and cartilage are generally described under the term leg weakness or osteochondrosis. These changes involve erosion of the articular cartilage and alterations to the normal patterns of growth at the growth plates at the ends of the long bones.

The use of both vitamins and minerals in cases of disease problems to try and prevent the conditions have been singularly disappointing and it is doubtful if specific nutrient factors are involved.

Prevention

Lameness can account for significant losses in growing pigs either because the pigs are unfit to travel on welfare grounds and require to be destroyed, or they are part or totally condemned at slaughter. Early identification of lame animals and their removal to hospital pens for treatment is a vital part of the control and healing process. Stocking density and mixing are the two major factors that precipitate traumatic disease.

Infections can also account for considerable losses particularly from tail biting and septicaemias that arise during immuno-suppressive diseases such as PRRS, EP and SI.

If there is a lameness problem on the farm it is necessary to identify the common problem and then refer to the relevant disease or diseases.

Consider the following:

• If more than 2% of pigs are recorded lame per month further investigations are necessary.
• Keep records of the time lameness occurs, which house the pig is in and if possible the visual appearance of the lameness.
• If lameness involves the foot look closely at floor surfaces.
• Look for marks or scarring on the skin that might indicate external damage due to fighting.
• Look for cuts or breaks in the skin related to sharp projections from the environment. The position of these on the body of the pig will indicate the height at which these are occurring. Typical examples are worn metal feeding troughs, worn metal pen divisions and bad slats.
• If there is a high incidence of leg sores associated with fractures assess the conditions precipitating leg weakness.
• Identify the most common recurring condition and refer to it using the index in this chapter.
• Consider specific diseases.