Shocking to see how much ignorance is displayed by what I'm assuming, are Pakistani Muslims. This slaughter is not acceptable and DOES NOT fall under the category of Sadaqa.
This backward practice of slaughtering a black animal is to ward off evil and bad luck. That makes it both an act of shirk and bid'ah and therefore sinful. That is a fact, irregardless of what good comes of the meat.
What are PIA going to do when they crash a B777 or A320? Slaughter a 100 black goats?
Only if a non-descript (colour) animal was slaughtered with the intent of only pleasing God would the sacrifice be acceptable.