Exploring the replacement rate of breeding sow herd

The annual repcacement rate of the sow population is actually a problem of "lifespan of the sow" as well a bioeconomic problem of the appropriate parity structure needed to achieve the targeted PSY level. The impact factors that affect the renewal rate or the longevity of sows have genetic factors, and more are non-genetic factors. The main reason is that the lifespan of sows cannot be measured within nucleus herd, nor can it be directly included in the complex selection index, along with the low heritability from 0.05 to 0.25. Therefore, the major measures for improving sow longevity or reducing the replacement rate are gilt development and selection standards, feeding management on body condition, reproductive management, which are recognized by developed countries with high level pig production. Genetic selection and selection of sows with integrity of legs and hooves are important indirect selection methods for improving the longevity of sows.