Veterinary Procedures in Ponyplay.

Introduction
Medical play is quite common in BDSM, and so it should not be surprising that veterinary play is not uncommon in the BDSM world of human ponies and pets. A standard veterinary check-up for your pony might consist of a thorough physical examination. Of course there are many more possibilities here such as collecting semen for testing from your male pony either through a phantom mare or through electroejaculation. Alternatively, for female ponies, a vaginal exam might be necessary prior to breeding. And of course, ponies' need to have dental exams (just like their bio-equine counterparts), which often require keeping the pony's mouth open wide while the vet is working.

Veterinary Procedures:
Physical Exam - Depending on what attracted you and your pony to ponyplay, and the resulting headspace created, a physical exam can range from sensual through mildly uncomfortable all the way to downright painful. When giving your pony a physical exam, you will usually be more detached than when you are grooming your pony. However, in some ways a physical exam is more intimate than grooming. I will give an overview of a general physical exam which I encourage you to modify to suit your taste and particular flavor of ponyplay.
Dental Exam - Giving your pony a dental exam can be fun for you and your pony. As with everything else in ponyplay, a dental exam will not appeal to all ponies or their owners/trainers/vets. However, for those to whom this does appeal, I encourage you to give it try. If you are a very oral pony (like me), I think you will enjoy it.
Catheterization - Catheterization in ponyplay is most often used as a form of bladder control. Once inserted and fixed in place, the catheter can be used to force continued emptying of the pony's bladder, or, alternatively, to prevent emptying of the pony's bladder. In fact, a urinary catheter can actually force more fluid (usually sterile saline) into a pony's bladder. This will "force fill" a pony's bladder. This can cause immense pain since the bladder can be completely filled with fluid and then closed off to prevent any emptying since the catheter is the only way the fluid can get out.
Castration (Gelding) - Note: I am talking about mock castration here. However, there are quite a few male ponies that identify as geldings, so it is appropriate to discuss castrating your intact ponyboy so you have a nice more manageable gelding. The threat of gelding a ponyboy is scary enough, but when he's tied down and the equipment comes out, castration play will really mess with his head
Rectal Exam - you and/or your pony's vet will examine your pony's rectum using your finger(s), or your hand if you really want to emulate the bio-equine world ;). This is usually done in the stocks to prevent the pony from being able to move away.
Branding - A hot piece of metal is used to create a permanent mark (usually a specially designed, unique symbol) on the pony. A brand in ponyplay can serve as a mark of ownership. It can also serve as a mark of status since certain brand designs/symbols might only be applied to ponies of a particular breed and even then, perhaps only to ponies representing the best of that breed.
Lip Tattoos - Lip tattoos are most commonly used on registered Thoroughbreds (bio-horse) as a form of identification. In ponyplay, a lip tattoo may also applied to the inside of the lips but can be on either the upper or lower lip. Moreover, a ponygirl (or ponyboy) is obviously may decide to have words or phrases may instead of the standard codes used on Thoroughbreds. Lip tattoos are not terribly uncommon as a form of body art and can be applied by a professional artist if a pony's vet is not comfortable applying the tattoo.
Needle Play - also referred to as play piercing, involves the insertion of a needle underneath the skin. Usually this entails both an entry and exit point for the needle. If performed in this manner, it is just like having a piercing except that no jewelry gets threaded through. Less commonly, there will be only an entry point with the tip of needle remaining under the skin (though this is usually associated with injection or infusion play). One way to incorporate this into your ponyplay/veterinary play scenes is as "acupuncture" treatment for your pony (quite a few bio-horse veterinarians offer equine acupuncture, so this is not an unrealistic veterinary procedure for a bio-equine).
Injection and Infusion - Injection/infusion play involves insertion of a standard hypodermic needle under the skin followed by injection or infusion of sterile saline. In ponyplay (and petplay), a pony's vet may inject a small volume (~ 1-5 mL) of sterile saline as a "vaccine". The effects of injection play are mostly psychological (depending on the injection site and diameter of needle used). However, infusion play involves larger volumes of fluid (up to 1L) and is often administered into the scrotum, labia, or breasts. Infusion play will stretch/inflate the area creating heightened sensation. The saline can take up to several days to be completely absorbed.
RFID (microchip) Implantation - Implantation of radiofrequency identification (RFID) microchips under the skin of animals (horses, dogs, and cats especially) is becoming more common as way in which to identify the animal. This can easily be done in humans as a part of ponyplay. This is one of those things that will probably only appeal to a very select few ponies or puppies, but it's worth including for completeness.

Veterinary Repro:
Please do not actually perform artificial insemination without the aid of a human physician and always have safe sex.
Milk Collection - performed on female ponies to milk for testing usually via a mild vacuum pump.
Semen Collection - performed on male ponies to collect semen for testing either via an artificial mare or electroejaculation.
Washing for Breeding - done on both male (cleaning the penis) and female (cleaning the perineum) ponies prior to breeding.

Veterinary Equipment:
Vet Wrap - a self-sticking bandage material available in a wide assortment of colors. Can be used to restrict movement or even retrain your pony.