Female cattle are cows, male cattle are bulls. But what word do you use if you don't want to specify an animal's sex?
The truth is that there is no noun in general use that refers equally to a cow or a bull.
Zoologists use two terms. The first is 'ox', which is often restricted to animals of the genus Bos (i.e. the wild cattle - gaur, banteng, yak, aurochs, and kouprey - as well as domestic cattle). In popular use, though, the word 'ox' often refers to a castrated male animal, so that isn't a perfect solution. The second zoological term is 'bovine', which is used as a noun to refer to any animal of the wider group that comprises cattle, buffaloes, and bison. But this would be a strange choice in most general contexts.