Abstract

This retrospective cohort study characterized death occurrences in female pigs in commercial herds, examined the survival probability for served females, and quantified factors associated with by-parity mortality risks for farrowed sows. The cohort data from herd entry to removal included 558,486 first service records of 113,517 females in 121 herds, served between 2008 and 2013. Two herd categories were defined on the basis of the lower 25th percentiles of herd means of annualized lifetime pigs weaned per sow: low-performing herds and ordinary herds. Two-level survival analysis was performed for served females to obtain by-parity survival probabilities (gilts and parity 1-6 sows). Also, log-binomial regression models were used to examine risk factors and ratios associated with mortality risks for the seven parity groups farrowed in either spring, summer, autumn or winter. Overall mean mortality incidence rates were 1.22 and 5.30 pigs per 100 pig-days of observation for pregnant females and farrowed sows, respectively. Survival probabilities for served females rapidly decreased by 2.3%-3.7% around farrowing in all parity groups. The lower survival probabilities were associated with increased age at first-mating, females in low-performing herds, sows farrowing more stillborn piglets and sows having weaning-to-first-mating interval of 7 days or more (P < 0.05). Mortality risks were assessed for herds, served month, WMI and stillborm piglets. Increased risks were associated with summer farrowing, low-performing herds and more stillborn piglets (P < 0.05). We recommended that producers individually monitor high risk female groups, and provide prompt treatment to any females with problems.

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