I think that if she goat is pregnant and you find out after qurbani then qurbani is not valid for eid. So maybe just to be on safe side, people dont slaughter she goat.
now why cow and not buffalo, that I am not sure. Maybe meat is more tender plus buffalo are used farming also
Agreed,
& Uze ghareeb bakron py tanz kerny ko ji nahi chahta*:D*