Each year, the replacement heifers entering the herd get a freeze brand on their hip. This brand, which matches the number on their eartag, is applied using a set of bronze numbers that have been super cooled in liquid nitrogen, and applied to the hide that has been clipped and prepped with alcohol.
The temperature of the brand destroys the pigment producing cells in the hide, and when the new hair grows back, it comes in white. This makes the numbers easy to see against black and red hided cattle. A freeze brand is easier to see from afar and comes in handy especially during calving season.