This is a cryogenic procedure in which liquid nitrogen is applied to the breech and tail area of a sheep to increase the area of bare skin and reduce the possibility of flystrike. This is considered preferable to mulesing which is the surgical removal of skin the area. Steined lambs recover much faster. There are various prohibitions on mulesing which do not apply to steining so that wool from steined sheep can attract a premium price.
The process has been developed by Victorian vet, John Steiner.