Epidemiologic studies of risk factors for sow mortality and removal

This thesis includes six studies conducted to answer questions concerning aspects of sow mortality and removal. Factors included herd level risk factors, reproductive performance parameters, leg conformation scores, presence of injuries and their relationship with stall characteristics, and the effect of a common analgesic used in sows at farrowing.; The first objective was to quantitatively describe sow removal from 49 breeding herds with a common genetic base. The outcome measure was derived from computerized records and was highly correlated with actual removal rate as calculated from a cohort of individual sow records available from 25 of the herds. Annual sow mortality and culling rates averaged 11.3% (SD 4.2%) and 41.7% (SD 11.9%), respectively. The second objective was to identify herd-level risk factors associated with sow mortality in the selection of herds described in objective 1. Absence of gilt isolation at the farm, occurrence of a clinical outbreak of swine influenza virus and presence of sows treated with antibiotics during lactation were found to be significantly associated with increased sow mortality.; The third objective was to determine the association between selected production measures and sow annual mortality rate. Pre-weaning mortality was positively correlated, possibly reflecting a relationship with the stockpersons' ability to detect sows and piglets at risk of dying at the farrowing room.; The fourth objective was to determine the association between conformation of gilts at the time of selection and their retention rate through 2 nd parity. Gilts with undesirable back leg scores were at a higher risk of premature removal.; The fifth objective was to determine the association between presence of skin lesions in sows in one herd, leg injuries and claw lesions with premature removal from the herd. No association was found between injury score and sow removal, stall type or removal due to lameness.; Finally, the effect of aspirin randomly assigned to sows in one herd during farrowing and its influence on longevity, wean to 1st service interval, and lactation length was determined. No protective effect was found in the outcomes analyzed for sows assigned to aspirin compared to controls.