Housing and flooring may increase the risk of removal especially with crowding and raising replacements on slats in the finisher. This is because younger animals may have marginal nutritional problems, be poorly selected for conformation, require different management or environment vs. older sows and also because osteochondrosis most often is seen at 6-15 months of age. Older sows more likely to have foot problems. This includes mastitis, agalactia, low milk production, poor mothering ability and overlaps with inadequate performance such as low weaning weights and high pre-wean mortality. The average age is 4.6 litters but parity 2's are prone to culling due to mastitis.
Death rates tend to be higher in larger herds.
There is variation due to differences in management, nutrition, environment and culling policies. Euthanasia should be included in the death category. High levels of euthanasia may indicate a failure to identify and quickly treat sick sows. In Canada, higher mortality occurs in the hot summer months. Older sows, rough movements, noise, excitement, rapid intake of food and water, omitting a meal, fineness of grind have roles.