Shoulder lesions are most commonly observed in sows during the weeks following farrowing. Long periods of lying combined with poor body condition can increase the likelihood of sows developing shoulder sores. The prevalence of shoulder lesions varies greatly depending on farm and sow factors, with anywhere from 10 to 50% of sows being affected. Shoulder lesions, also referred to as shoulder sores or ulcers, typically appear as a circular sore on the upper shoulder.
In sows, shoulder lesions appear over the scapula, where the amount of soft tissue between the skin and bone is insufficient to distribute external pressure. Lying laterally (such as during nursing bouts) puts pressure on this area, and prolonged lying can restrict blood flow and result in localized tissue damage. Shoulder lesions in sows are comparable with pressure ulcers in humans, also known as bed sores. Once they have developed they are difficult to treat, and will often return during the next lactation. In practical terms this means sows are at their highest risk for developing lesions in the weeks after farrowing as they can spend over 90% of their time lying during this period.
The first indication of a shoulder lesion forming is reddening of the skin. The skin may become damp and flies can be attracted to the area. If the problem goes untreated, the sore can quickly progress to an open ulcer, and in extreme cases, the underlying bone may be exposed. The occurrence and severity of shoulder lesions varies greatly from farm-to-farm, reflecting the multi-factorial nature of this problem.