Interval from last insemination to culling: I. The genetic background in crossbred sows

Improving longevity of sows is hampered by the lack of accurate and early recording of factors that contribute to reduced longevity. Besides, phenotypic data of parity number at culling or culling reason are potentially collected in purebred individuals, while these animals are not able to show full potential of their longevity due to EBVs, which makes the culling to take place earlier. In contrast to crossbred animals, of which usually very little information is collected, as phenotypes are expensive and difficult to obtain. Longevity is influenced by several culling reasons of which fertility and leg weakness are known to be the most important, although culling reason is unknown or unreliably recorded in crossbreds. To distinguish different reasons for (in)voluntary culling, interval from last insemination to culling (IL2C) might be able to function as an indicator, which could potentially enable us to breed for sow able to fulfil a complete production cycle. The aim is to quantify and understand the mechanism of parity number at culling by analysing the IL2C, in relation to parity number at culling. The results show that IL2C is a heritable trait that can be used in selection, in addition to parity number at culling. Parity number at culling and IL2C are not significantly correlated, which shows the potential to take both traits into account in breeding. By combining improvement of IL2C with improved longevity, economics and welfare of crossbred sows will even further be increased.