Date Full Report Received02/25/2010
Date Abstract Report Received02/25/2010
Funded ByNational Pork Board
Lameness has long been identified as a concern in sow herds. It is usually recognized as a painful condition and as potentially detrimental to the future productivity of that sow. Lameness is recognized as one of the main causes of culling and is often frustrating to herd managers and stock persons in that it is difficult to treat and control measures are infrequently identified. Studies in sow lameness are infrequent and are limited by challenges in the creation of repeatable measures for epidemiologic studies.
In this study, our aim was to study and identify methods of measuring lameness and its underlying mechanisms and evaluate culling strategies associated with the identification of lameness. Though there is no gold standard, statistical methods can be used to identify the identifiers of lameness that can be repeatable across sows and herds.
In previous studies we have shown that the use of pain killing drugs eliminates signs of lameness in the great majority of sows. This is an indicator that pain is the major driving force for lameness (as opposed to physical defects). Therefore we used indicators of pain that have been used somewhat successfully in human evaluations of pain. In our hands we did not find a chemical test for pain probably due to the fact that lameness is a chronic condition and the body appears to compensate for the effects of pain.
Conversely, the examination of the gait of sows was productive. Subjective classification of lameness is repeatable especially if minor signs are ignored. Focusing on particular behaviors such as head dipping and identification of affected limbs can add to the accuracy of diagnosis. For sows in stalled housing, weight shifting is also accurate, but does not identify as many sows as lame as the examination of gait. Claw lesions, especially cracks in the wall of the hoof were also correlated with lameness.
As we examined these indicators of lameness, we found that they predicted culling only when there was an adequate supply of sows and gilts to meet the breeding target. Otherwise, they were retained and showed a significantly lower level of productivity. In financial analysis, the output reduction due to this lower reproductive output justified replacement in almost all cases.
This study shows that lameness is a real problem on sow herds and can be addressed by regularly assessing lameness and treating sows where possible. This will not only increase the productivity of the herd but also the well-being of sows and should be a basis to identify preventive and therapeutic interventions.
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