Additionally, when appropriate, a complete necropsy examination should also be conducted by a veterinarian to assess the full extent of the condition, to collect samples for laboratory testing and to make treatment recommendations.
During necropsy, long bones, ribs and several joints are typically examined to assess the condition of the bones, cartilage and surrounding soft tissues.
In some cases, submission of distal portions of rib bones for specialized laboratory testing can provide useful information in the overall assessment of bone and cartilage health. The development of lameness in pigs is influenced by several, often overlapping factors in each stage of production. In the weaner-grower stage, pigs are typically more susceptible to infectious insults that lead to lameness; and this increased susceptibility is due to factors such as waning maternal immunity, movement and mixing of pigs, and increased stress caused by weaning.
Lameness of pigs in the late grower-finisher stage is also influenced by the factors mentioned previously, in addition to nutritional imbalances. Trauma can result in fractured bones, joint dislocations or soft tissue damage; and can be caused by the sow, or during such activities as catching, restraining and transporting piglets. Polyarthritis often presents as lameness and swelling of multiple joints and is typically caused by bacterial infection.
Soft, thin skin and a lack of soft tissue surrounding joints in neonatal piglets predisposes them to skin abrasions which can result in direct introduction of bacteria into joints. Additionally, polyarthritis can also be a sequela to systemic bacterial infection i. Litters from gilts may be more susceptible or more severely affected due to reduced maternal immunity. The bacteria most commonly associated with polyarthritis in neonatal piglets include Streptococcus suis , S.
However, other streptococci, staphylococci, other coliforms and actinobacilli can also cause infections. The joints most commonly affected are the carpal i. Concurrent conditions such as pneumonia and meningitis i. Foreign animal diseases should also be considered in outbreaks of lameness when the clinical history and signs are suggestive.
Trauma due to improper flooring or other environmental conditions or during transport can result in lameness. If bone fractures are observed in several animals in the late-finishing stage, an underlying nutritional imbalance or deficiency should be considered as an underlying cause. Haemophilus parasuis , Actinobacillus suis , Mycoplasma hyosynoviae , M. These bacteria can also cause septicemia in post-weaning pigs. Septicemia and arthritis caused by S. Other bacteria such as A. The joints most commonly affected by arthritis in the post-weaning period are the same as those most commonly affected in the neonatal period; and the characteristics of the joint fluid and joint tissues are similar to those described previously.
The exception to this is arthritis caused by M. Additionally, the amount of joint fluid is increased in affected joints, but it is usually not as cloudy; and the joint tissues are typically only mildly thickened and slightly reddened. Nutritional imbalances and deficiencies that lead to altered bone growth and subsequent deformity of long bones and articular cartilage are important causes of lameness in post-weaning pigs. In adults, these changes can result in decreased bone strength.
Each of these conditions are defined by the growth stage of the affected animal in combination with distinct microscopic changes observed within bones and articular cartilage. Only the two most common conditions will be covered here. Rickets, a metabolic bone disease of growing pigs that are commonly 2- to 6-months old, manifests as swollen joints and lameness, particularly affecting the carpus, shoulder, elbow and stifle joints.
During necropsy, folds and fissures in articular cartilage, and thickened and irregular growth plates may be observed. Additionally, the distal ends of rib bones may be widened; and under pressure, the ribs can be soft and bend rather than snap.
Its anteromedial portion is mainly composed of fibres taut in extension with some additional fibres taut in intermediate positions. The PCL is not subdivided. Most of its fibres are taut in flexion and some in intermediate positions. Its guiding bundle is consistently taut in all joint positions.
The functions of the cruciates basically are the same in humans and in pigs, namely in guiding the joint and in restricting motion. It must, however, be borne in mind that the maximal extension of the pig corresponds to a human flexion of 30 degrees.
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