I am going to say if he ate it to the stubs, you won't get any early bloom, might not get much of any bloom.

I would get a set of bars or wire screen, so horse can't reach out again to eat the Hydrangea. Or move the shrub so he can't reach it at all.

Hydrangea is on the list of plants that are bad for horses. Here are a couple sites:

http://www.library.illinois.edu/vex/toxic/hydrga/hydrga.htm

http://www.aspca.org/pet-care/poison-control/plants/hills-of-snow.html

Hydrangeas are lower down under shrubs, show toxicity levels:

http://www.aragriculture.org/horticulture/ornamentals/toxic_plants.htm

I sure hope the deer is the culprit who ate your bush, not the horse. But if horse can reach the bush, you need to put something up to prevent a problem from happening. Horses LOVE woody stems in winter seasons, when they have nothing else to chew on, so a danger potential is there.

The bush is not in a area where the horses normally have access unless someone leaves the gate open and they get into the yard. He loves looking at himself in the window above the hydrangea and talking to the pretty horse in the window. That always how I know he,s out there. He gets very loud and strikes at the house. A deer could have done it but he was out that morning so I really think it was him. Thanks for posting the links on the other thread I didn,t now maple trees were toxic . We have several in the pasture. They always have free choice hay and grass but you never know when one is going to try something. He hadn,t touched a hydrangea bush in 23 years and just did.