Herd and sow-related risk factors for mortality in sows in group-housed systems.

Mortality of sows is a major problem for pig production worldwide. In this study, we used hierarchical multivariable logistic analyses to investigate different risk factors for mortality at the sow and herd level in herds with group-housed pregnant sows. Data included 3652 pregnant and 1266 lactating sows from 34 sow herds. A clinical examination for 16 clinical signs was carried out for each sow, and information about 16 herd related factors was obtained by interviews. Farm records were used to obtain information about whether or not sows died suddenly or were euthanized within 3 months after the clinical examination. Factors increasing the risk of sow mortality in the gestation unit were solid pen floors (OR=1.87), presence of vulva bites (OR=1.73) and unwillingness to stand when approached (OR=1.62). Factors increasing the risk of sow mortality in the lactation unit were pale vulva color (OR=12.69), body leanness (OR=4.11), and presence of shoulder ulcers (OR=2.89). The estimated between herd variation was small. Thus, the findings for the sow level variables may be generally applicable for sows in herds with group housed systems.