I know my local TSC has their own brand (Dumor, (sp?)
) of hay stretcher. It is a 12% protein, 1.5% fat and 32% fiber. I have not bought it but have looked at it, it reads as if it is a pellet feed. It is said to be able to be fed soaked (wet) or dry. Sounds kind of like the beet pulp idea to me...
I'm not convinced this is the way to go as TSC also has really nice quality cubes of alfalfa, timothy or a mix of both of these readily available and for about the same price.
Having an option and thinking about the "what ifs" is great... so far though, I am able to get good hay and will stick with that. Thankfully, I don't have a horse with limited abilities to chew and digest hay itself...that would add another dimension to my feeding needs for sure.
For now though, hay bales then I would do hay cubes myself.