Length of productive life of crossbred sows is affected by farm management, leg conformation, sow's own prolificacy, sow's origin parity and genetics.

The purpose of the current study was to determine if the parity of the litter in which a female was born and the number of pigs within that same litter are associated with future length of productive life (LPL). An additional objective of the study was to examine the associations of leg conformation (evaluated at approx. 100 kg of live weight), age at first farrowing, litter size at first farrowing, and age and backfat thickness at 100 kg on LPL in the Finnish crossbred (Landrace × Large White or Large White × Landrace) population. The data analysed contained information on 11 761 sows, and proportional hazard model (Weibull) was fitted on the data using the Survival Kit. Log likelihood tests were utilised to determine if the individual effects have a significant impact on LPL. Farm conditions and management were identified as major factors impacting on LPL ( P < 0.001). Other factors significantly ( P < 0.001) associated with LPL were leg soundness score, age at first farrowing, and litter size at first farrowing. The better the leg score, the younger age at first farrowing, and the larger litter at first farrowing, the longer sows tended to remain in the herd from the present. Although sows born in litters first, second, and sixth parities had slightly greater risk of being culled when compared with sows born in litters from the other parities, the effect was not statistically significant. Sufficient genetic variation exists in the population evaluated in this study for LPL (h2 = 0.25), such that it will be possible to improve LPL through traditional selection methods in an efficient breeding programme. Thus, there are many factors which impact on LPL, and possibilities to improve all of them should be considered in order to improve the economics and animal welfare of modern pork production operations.