5Gjein H, Larssen R B. Housing of pregnant sows in loose and confined systems-a field study. 2. Claw lesions: morphology, prevalence, location and relation to age[J]. Acta Vete Stand, 1995, 36:433-442.
6Sukumaran S A, John D, Marrin S. Claw lesions and sow housing systems[J]. Inter Pig Topics, 2008, 23:7-8.
7Stalder K J, Karriker L V. The impact of gestation housing system on sow longevity[C]. Proceedings of the Sow Housing Forum, Des Moines Iowa,2007.
8Anil S S, Anil L, Deen I. Ef{ect of lameness on sow longevity [J]. J Am Vet MedAssoc, 2009, 235:734-738.
9Heinonen M, Oravainen J, Orro T, et al. Lameness and fertility of sows and gilts in randomly selected loose-housed herds in Finland[J]. Vete Record, 2006, 159.-383-387.
10Boyle L, Leonard F C, Lynch B, et al. Sow culling patterns and sowwelfare[J]. Ir Vet J, 1998, 51:354-357.
