It depends by what you mean by "they." Please be more specific when asking these types of questions!
A cow. Or, if you want to go into specifics, a dairy cow.
It gives more milk than what it would normally produce for its calf. That's what constitutes a cow for being a dairy cow.
Dairy
The dairy cow.
That all depends on the breed. Are you asking about a dairy cow or a beef cow, and what breed of dairy or beef cow?
Dairy cattle like Holsteins, Brown Swiss and Jerseys.
A dairy cow would die a matter of a few weeks before she even gets to the point where she is deemed "feral." I would see a beef cow becoming feral, yes, but not a dairy cow.
There's not really an answer... You just call it a cow...
cow
A farm
No. The biggest type of bovine is typically the beef cow. There are beef cows around that weight more than a big dairy cow, and that can be upwards of 2000 lbs or more.
It takes less animals to produce more milk with a cow-based dairy than a sheep- or goat-based dairy. One dairy cow will produce more milk over a period of time than one goat or sheep.