A farrowing crate was designed with sides spaced well apart (1150 mm) at the sow's standing height but angled inward near the floor to restrict the sow's lying area and to prevent the sow from dropping suddenly onto one side. Survival and body-weight data were collected for 20 farrowings in the prototype crate and for 18-20 farrowings in each of 3 other crate types. No significant differences were found in stillbirth rate, other deaths to 14 days, or average piglet weight gains, but gains were somewhat more variable in one of the conventional designs which interfered with the piglets' access to the teats. The principle of inward-sloping crate sides may provide a less restrictive alternative to conventional farrowing crates, but large-scale testing is needed.
Fraser, D., Phillips, P. A., & Thompson, B. K. (1988). Initial test of a farrowing crate with inward-sloping sides. Livestock Production Science, 20(3), 249-256.