Lameness is a major disease of factory farmed pigs. Although lameness can be caused by congenital or developmental abnormalities, most lameness in farmed animals is caused by pain associated with infections, trauma-related injuries, or underlying metabolic diseases. The most common limb lesions in weaners, finishers and sows are calluses, swellings, wounds, external abscesses and bursitis. Stress and ill-health can also lead to lameness. Trauma is by far the most common cause of lameness in the dry sow, from point of weaning to point of farrowing. Environmental trauma to the coronary band area and to the sole or wall of the foot results in penetration of the sensitive tissues, infection and lameness. These foot conditions are called ‘bush foot’ and ‘foot rot’ (82).
Lameness is the third most common cause for treatment with antibiotics in weaner and finishing pigs.
Housing type is one of the major factors influencing lameness on commercial pig farms. It influences the amount and type of movements pigs can make. Individual housing in gestation stalls contributes to lameness via reduced bone strength and muscle mass, and joint damage due to lack of exercise.
Flooring type can be a major influencing factor on lameness and claw health as the pig has continual contact with the floor surface.
Osteochondrosis is a painful and debilitating leg disorder that causes lameness in pigs. It is attributed to pigs being forced to grow too fast and being housed on hard, slatted floors. Cracks and crevices arise in the cartilage layer at the hock, elbow, shoulder and hip joints.
An ideal floor for pigs should be soft, clean, not slippery and not abrasive; the surface should be even and without sharp edges. In the majority of pig units, slatted concrete floors are used and such floors increase the risk of lameness. Slatted floors present some disadvantages to the animals, such as an uneven walking surface and the lack of bedding.
Inappropriate slatted flooring can cause widespread lameness in pigs. Current UK legislation and Quality Assurance schemes such as Red Tractor allow fully slatted flooring in finishing units. This pig was filmed in 2015 by Viva! © Viva!
Foot rot is exacerbated by the urine soaked, unhygienic conditions in which many pigs live. The lesion of the foot is invaded by bacteria, causing it to go septic. The area is often ulcerated and very painful for the animals. If abscesses develop, the leg is held off the ground. Secondary abscesses may form in other areas, for example the brain, liver or spleen.
Lameness is also caused by overgrown claws (caused by housing pigs on muddy ground with little opportunity to exercise); laminitis (in boars and heavily pregnant sows), and erosive foot lesions.
Lame pigs have very poor welfare because they are in pain, suffer discomfort, are at a disadvantage when it comes to competing for resources, are more susceptible to other diseases and consequentially they fail to thrive/reproduce. The considerable impact of lameness on pig welfare is too often overlooked on pig units. Often with lame sows, the only ‘treatment’ is to cull her after production of the litter.
Animal production expert, Lean, states (45):
“Sows kept in close confinement and/or on slats may become so lame and in obvious pain that there may be no other recourse but to send them to slaughter, assuming they are still able to walk”.