Freeze brand

Freeze branding (sometimes called CryoBranding and the resulting brands, trichoglyphs^[1]) is a technique involving a cryogenic coolant instead of heat to produce permanent marks on a variety of animals.^[2]

The coolant is used to lower the temperature of a branding iron such that its application to shaved skin will permanently alter hair follicles. The intense cold destroys the pigmentation apparatus in the animal's hair follicles, leaving all subsequent hair growth without color. This creates a high-contrast, permanent mark in the shape of the branding iron's head. A longer application of the cold iron can also permanently remove hair, and is used on white or pale animals. In these cases the loss of hair leaves a patch of hairless skin in the shape of the brand.

The technique is most commonly used as an identification mark for ownership, although it finds application in biological studies of wild animals as well.^[3] Freeze branding is most often used on mammalian livestock with smooth coats such as cattle, donkeys and horses although it has been used successfully on a wide variety of other mammals, as well as frogs, newts, snakes, fish and even crabs.^{[4][5][6][7][8]}

Freeze branding is often seen as a more ethical alternative to traditional hot branding, so much so that experts have called for the prohibition of hot branding in favor of the cryogenic technique.^[9] Hot branding involves the use of an iron stamp heated to around 500 ºC (930 ºF), a temperature sufficient to destroy all three layers of an animal's skin and leave a permanent scar.^[10] This process is extremely painful and can traumatize the animal. Freeze branding gained popularity in the middle of the 20th century as a less painful way to permanently mark and identify animals. There has been debate as to whether freeze branding is truly less painful than hot branding, but scientific studies conducted to compare the relative pain of the two methods have concluded that freeze branding is indeed less distressing to the animal being marked.^[11]

Freeze brands are made for a variety of purposes. For example, they are used to indicate that an animal belongs to a particular herd, all members of which are marked with the same brand. They are also used to indicate via a unique pattern that an individual animal is a particular person's or ranch's property. Freeze branding is also used to tag wild animals that will be recaptured for later research.^[7]