3. The murderer of a Brāhmaṇ becomes consumptive, the killer of a cow becomes hump-backed and imbecile, the murderer of a virgin becomes leprous,--all three born as outcastes.
The Garuda Purana, by Ernest Wood and S.V. Subrahmanyam, 
In Hinduism, does the word "cow" refer to just one type of domesticated bovine animals, the Indian cattle or is it more of a concept that applies to all domesticated milk-producing animals?
For example, is the water buffalo (pictured below) considered a cow?
What about camels, goats and other milk-producing animals?
If buffaloes, camels and goats are not "cows", then does it follow that there's no sin associated with killing any of these for their meat or at least it's less sinful than killing a cow (gohatya)?