Breeding ponies are can be of either male or female and the sex can be simulated or real. The difference between breeding ponies and pleasure ponies is breeding ponies have sex with other ponies as opposed to their owners/trainers (at least during a scene). Two (or more) breeding ponies may be bred in front of their owners/trainers and even other people.
The opportunity for incorporating veterinary play, especially reproductive exams, is vast for breeding scenes. Moreover, preparation for breeding also provides ample opportunities for scenes, such as cleaning the pony or ponies, - especially the reproductive parts :) - and restraining the pony to be bred as well as the stallion.
While some human ponies are able to be bred freestanding, it's common to have the pony being bred restrained so that it does not injure the stallion by inadvertently kicking or bucking. Breeding benches are good for this since they keep the pony to be bred prone with their limbs pulled apart and tied to the corners of the bench. A strap or two around the upper body is also useful to limit the pony's movement, and padding on the bench makes in comfortable for the pony when performing a long (or repeated) breeding scene.
However, a simple pair of hobbles will also suffice to prevent kicking during a breeding scene. My favorite is strappado bondage combined with hobbles. This bondage is very restrictive and the pony will be unable to move much - any movement will also make the bondage significantly more uncomfortable, further discouraging movement. It also has the added advantage of pulling the pony's upper limbs well out of the way of the crotch area, allowing easy access for the stallion.
It is also often a good idea to restrain the stallion in some way to prevent him from injuring the pony being bred. Typically his arms will be bound behind him, his legs hobbled, and either a stud chain or a harsh bit in his mouth. This should allow him sufficient motion to breed but still keep him under control.