The term "cattle" is a plurale tantum, which means it can only be used in the plural and not in the singular. There is no universally accepted singular generic word for "cattle" in modern English, other than the sex- and age-specific terms such as cow, bull, steer, and heifer. Historically, "ox" was not a sex-specific term for adult cattle, but generally this is now used only for draft cattle, especially adult castrated males. Some people use "cattlebeast" or "beef" as a singular term, but these are not widely accepted. Therefore, if you need to refer to a single animal, you can use the sex- and age-specific terms such as cow, bull, steer, or heifer, depending on the animals characteristics.