8Engblom L, Lundeheim N, Dalin A, et al. Sow removal in Swedish commercial herds [J]. Livestock Science, 2007, 106(1) : 76-86.
9Sasaki 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.
10Lucia 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.