Athena said: ...In a horse that is bred with a fairly level head or neck set, high head carriage tends to hollow out the back.

Perhaps I was unclear. Threecorners said that a horse whose neck came out of the shoulders too high, could not collect and use its hind end properly to reach under itself. My point is that dressage horses neck joins higher on the shoulder than a Western Pleasure horse but has no trouble coiling the loins and reaching under his body with his hind legs. Yes, if a horse, regardless of how his neck joins his shoulders, holds his head too high to coil his loins, he will go hollow-backed. But just having a neck that comes out of the shoulder higher than a WP horse will not make it impossible for him to collect.

Susan