Lameness is the second commonest cause of culling in breeding sows after reproductive failure and can occur as a result of physical injury, infection or inherent leg weakness. Lameness incidence may be affected by both genetic and environmental factors, and is especially prevalent in confined systems such as stalls and tethers, which restrict the amount of exercise that the sows can perform. Confinement, with a corresponding lack of exercise, has been shown to affect bone strength in poultry but this weakness has not been documented in other species housed in confinement. The objectives of this experiment were to compare bone strength and muscle conformation in sows housed in two different dry sow systems.

A total of 18 non-pregnant Large White X Landrace sows of similar age, parity and genetic stock, were studied in two different dry sows systems: 1) permanent stalls (n=8) and 2) a large group with Electronic Sow Feeder system (n=10). All sows were weighed and following slaughter by pentabarbitone injection, the left thoracic and pelvic limbs were dissected and five forelimb and nine hindlimb locomotory muscles were removed and weighed. The muscles were chosen partly on the basis of perceived importance for locomotion and partly on the basis of ease of identification and removal. A proportional muscle weight was then calculated by dividing individual muscle weight (in grams) by total body weight (in kilograms). This removed any differences in muscle weight due purely to differences in total body weight between systems. The left humerus and femur were also removed, and were broken by a three-point bend test using an Instron Universal Tester.