Munk?
As I recall, the deal was that for all the equipment we sent over, there were no transportation vehicles suitable for use in the mountainous terrain. The U.S. mules were so much larger and heartier than those available in Afganistan, and could negotiate the steep hillsides and rocky slopes, that they were very much valued. ?Mammoth Jack? breeding...not sure.
The fact that the Afganistan patriots (interesting how designations change when your perspective changes, eh?) were not congregated in large groups like conventional armies allowed for small parties of troops to carry on mule-back the Stingers, food, water, etc...in areas that the Soviets would not or could not access.
With the advent of the Stinger, the Soviet technique of dropping squads off in rough terrain via helicopter became VERY expensive.
And, as you say, mules can be eaten.
Kis