What is one method of identification for livestock that uses a visible mark on the skin?

Branding is a method of identification for livestock that involves creating a visible mark on the skin using heat or cold to form a permanent symbol or number. This method has been widely practiced in livestock management for centuries because it allows for easy identification of animals within a herd, particularly in large operations. The branding process burns or freezes the skin to create a mark that is distinct and can be seen at a distance, making it effective for identifying ownership and helping in the tracking of livestock health and breeding history.

Although other methods like tattooing also create permanent marks, they are usually less visible on the animal's skin compared to branding. Tattooing often involves a series of inked numbers or letters placed in specific areas, which may not be easily visible unless the animal is handled closely. Collaring involves placing a physical collar around an animal’s neck, which is more common in pets. Electronic tagging relies on electronic devices for identification, offering a different approach that does not involve a visible mark on the skin. Thus, branding stands out as the method primarily characterized by visually identifiable marks on livestock.