Lameness in sows is a common cause for compromised animal well-being and economic loss to producers. Lame animals are likely to be unable to attain optimal breeding efficiency1 and may be culled before they attain their peak production. Locomotor problems are a major reason for culling2 in swine herds, with a reported culling rate of 15.2% in US swine herds.3 Sows culled because of lameness are removed at a younger age than those removed for other reasons.4–6 Early removal of sows from the herd results in lower mean litter size, number of litters per sow per year, and number of pigs weaned per sow per year, thus increasing the cost per weaned pig.5 The addition of new gilts into the system may also increase health risks to the animals currently in the herd.7 The authors of a study8 conducted in Germany reported fewer litters (< 3.0 litters for lame sows vs 4.5 litters for nonlame sows) and higher baby pig losses (27.7% for lame sows vs 12.4% for nonlame sows) in lame sows than in healthy sows. In that study,8 the financial loss associated with a lame sow to account for fewer pigs born, baby pig mortality rate, and early slaughter of sows was estimated to be 37 euros/sow ($52/sow).
Furthermore, lame sows receive extra scrutiny when shipped to market, which decreases the salvage value. Lack of analgesics and the high labor requirement associated with providing medications for individual animals in large herds add to the fact that prevention of lameness is a better option than treatment. Despite the high prevalence of lameness in swine herds, potential measures to minimize lameness and its adverse effects have been less thoroughly explored, compared with evaluations conducted for other diseases of swine. Although lameness is extremely prevalent in breeding herds, diagnosis can be unreliable because of the lack of a criterion-referenced standard. A recent studya on the sensitivity and specificity of lameness identification in sows as determined on the basis of gait abnormalities indicated that it was relatively easy to distinguish a severely lame sow from a healthy sow, but it was difficult to correctly distinguish a mildly lame sow from a healthy sow. However, early detection is critical in preventing the condition from deteriorating. Additionally, lack of observation of individual pigs for gait abnormalities is another limitation in lameness assessment in large swine herds. However, the movement of sows to farrowing facilities offers an opportunity to observe the gait of sows on most farms. Given that a severely lame animal will be culled or euthanatized if necessary, sows with less severe, chronic lameness can continue to persist in herds.
A better understanding of the effect of risk factors, including lameness, on sow productivity and longevity would augment efforts to minimize lameness in swine herds. The purpose of the study reported here was to analyze the association of lameness and performance variables with sow longevity by use of time-to-event analysis.
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PigCHAMP, version 4.10, PigCHAMP Inc, Ames, Iowa.
SAS, version 9.1, SAS Institute Inc, Cary, NC.
PROC lifetest, SAS, version 9.1, SAS Institute Inc, Cary, NC.
PROC phreg, SAS, version 9.1, SAS Institute Inc, Cary, NC.
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