Just do a google for 'free horse 3ds', as 3ds is the most common format for decent free models it seems. Then, pick your breed and discipline.
😉
Of course, you might end up with a Lippizaner like this one:
http://www.syntheticgraphics.com/meshes/lipp_horse.html
whose neck seems to be as big as her body barrel.
Some free ones here:
http://horse.turbosquid.com/3d-Models/3ds/max/xsi/c4d/obj
These cost $$:
http://www.the3dstudio.com/product_search.aspx?id_category_0=1&search=horse
If you don't have the 3DS In add-on, go to Help > Goodies to download it so you can import the models you find. Be sure to check the box for smoothing. If the models come with textures, the textures will be included in the created GDL object.
Karl
One of the forum moderators
AC 27 USA and earlier • macOS Ventura 13.6.9, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB