6Engblom L, Lundeheim N, Dalin A, et al. Sow removal in Swedish commercial herds [J]. Livestock Science, 2007, 106(1) : 76-86.
7Sasaki Y, Koketsu Y. Culling intervals and culling risks in four sta- ges of the reproductive life of first service and reserviced female pigs in commercial herds [ J ]. Theriogenology, 2010, 73 ( 5 ) : 587-594.
8Lucia Jr T, Dial G D, Marsh W E. Lifetime reproductive perform- ance in female pigs having distinct reasons for removal [ J ]. Live- stock Production Science, 2000, 63 (3) : 213-222.
9Stalder K J, Lacy R C, Cross T L, et al. Financial impact of aver- age parity of culled females in a breed-to-wean swine operation using replacement gilt net present value analysis [ J ]. Journal of Swine Health and Production, 2003, 11 (2) : 69-74.
10Engblom L, Lundeheim N, Strandberg E, et al. Factors affecting length of productive life in Swedish commercial sows [ J]. Journal of animal science, 2008, 86(2): 432-441.