1) Herd 
A Remuda is a herd of horses from which ranch hands select their mounts. The word is of Spanish derivation, for `change of horses` and is commonly used in the American West. The person in charge of the remuda is generally known as a wrangler. ==Necessity== West of the Mississippi River, ranches are larger in acreage than are the farms to the eas.....
[n] - the herd of horses from which those to be used the next day are chosen
noun the herd of horses from which those to be used the next day are chosen