Posted at Secrecy News (FAS Blog) - Special Forces Use of Pack Animals.

U.S. special operations forces typically make use of some of the most sophisticated military and intelligence gear available. But sometimes a "no tech" solution is the right one.

So, for example, Special Forces "may find themselves involved in operations in rural or remote environments... using pack animals," including horses, donkeys and mules.

"Pack animal operations are ideally suited for, but not limited to, conducting various missions in high mountain terrain, deserts, and dense jungle terrain."

An Army Special Forces manual (large pdf) provides instruction and doctrinal guidance for using pack animals in training and combat missions.

"This manual provides the techniques of animal pack transport and for organizing and operating pack animal units. It captures some of the expertise and techniques that have been lost in the United States Army over the last 50 years."...

The 225 page manual provides a basic introduction to the characteristics of each of the various pack animals, some rudiments of veterinary care, and miscellaneous lore....

The Special Forces manual has not been approved for public release, but a copy was obtained by Secrecy News.
Also see Chapter VII - Mounted Detachments of the Small Wars Manual.