Peter Balogh, Wojciech Kapelański, Hanna Jankowiak, Lajos Nagy, Sandor Kovacs, Laszlo Huzsvai, Jozsef Popp, Janos Posta and Angela Soltesz
The aim of this study was to compare the characteristics of the productive lifetime (PLT) of sows kept on two farms, from the aspect of reasons for culling. The study was based on data from animals from two breeding farms in Hungary, using the data of 3493 crossbred Dutch Large White and Dutch Landrace sows (DLW × DL) between their first farrowing until the time of culling (2006 and 2012). For six years, the annual culling rate for both farms averaged 45%. The most frequent reasons for removal on both farms were reproductive problems (40%, 51%), leg problems (29%, 23%) and mortality (19%, 15%). There was a significant difference between the distributions of reasons for culling on the two farms (χ2=41.7, P≤0.001). The distributions of reasons for culling differed in three periods of sow breeding (Farm A: χ2=264.7, P≤0.001; Farm B: χ2=511.1, P≤0.001). The percentage of main removal reasons decreased, whereas the frequency of culling due to age increased. Using survival analysis (Kaplan-Meier method and Cox proportional hazard model), significant differences were identified between the PLT of sows culled due to reproductive problems (P≤0.001), leg problems (P≤0.001) and old age (P≤0.001). Reproductive problems (HR: 1.34, P≤0.001) and leg problems (HR: 1.39, P≤0.001) were higher and culling due to old age (HR: 0.44, P≤0.001) was lower on Farm A compared to Farm B. There were no significant differences between the two farms in terms of mortality (HR: 0.99, P=0.923). Overall, the results can be useful for breeders of crossbred (DLW × DL) sow populations in more accurately defining their culling systems.