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.
Highlights
Decreasing the mortality risk in female breeding-pigs is critical to enhance maternal health and animal welfare in commercial herds, and it helps prevent decreased productivity, economic losses and reduced worker morale
In the few studies have looked at these issues, one recent study indicated that risk factors such as summer months or high outside temperature, and high parity number are associated with higher mortality risks for sows around farrowing (Iida & Koketsu, 2014)
The objectives of the present study were to characterize death occurrences in female pigs in southern European commercial herds, to examine multi-level survival probability for served females, and to quantify factors associated with by-parity mortality risk and risk ratios for farrowed sows
Summary
Decreasing the mortality risk in female breeding-pigs is critical to enhance maternal health and animal welfare in commercial herds, and it helps prevent decreased productivity, economic losses and reduced worker morale. A recent report showed that the annual death rate in breeding herds in the U.S.A. is 8.9% (PigCHAMP, 2015). Another U.S study showed that the mortality risk rose as the number of parity increased from 0 to 7 or higher (Koketsu, 2000). Both peripartum periods and farrowing events have been reported as major risk factors for sow mortality (Sasaki & Koketsu, 2008). No studies have examined and quantified any other possible factors, such as the number of stillborn piglets and being fed in low-performing herds
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