The methods described in pages are a theoretical discussion ONLY. Methods are discussed in only the broadest terms and I hold no qualifications in the fields discussed.
Because a method is listed here does not indicate that I approve or recommend it. In some cases, I definitely don't!
In using surgery as a method of shape-shifting, we are really talking about making a horse-shaped human. Surgery won't change the underlying genetics, unless advanced gene-therapy is also applied (see DNA Manipulation). It would also be difficult to introduce any radical size alteration, so we might be talking about turning someone into a Falabella (a miniature breed of horse that seldom exceeds thirty inches) rather than the sleek Arabian they dreamed of.
Nevertheless, surgery is capable of some miraculous things. Both hard and soft tissues within the body are very adaptable. Bones can be lengthened, shortened or reshaped; even replaced by artificial substitutes in some cases (although the need to do this is declining). Cartilage can be lab-grown from a sample and reintroduced to the body - this is regularly used today for such conditions as knee injuries.
Skin can be cultivated and grown from grafts. The body's abilities to repair damaged tissue mean that a small quantity of skin from a donor site can be made to cover a larger receiving site by perforating the graft and stretching it: the holes heal themselves.
Research resulting from the Human Genome Project strongly suggests that the body's healing abilities, which are a vital part of any surgery, can be enhanced by gene therapy. Our healing abilities when we are born far outstrip those same abilities when we grow older: this decline is a programmed sequence controlled by our DNA. Recent experiments suggest that lost healing abilities can be reactivated or even enhanced.
Shaping is of no value unless the body is functional. Organs, muscles and nerves must serve the new shape. It may be acceptable to leave the body's major organs to go on about their business largely undisturbed; we're going for cosmetic here. A body is of little use if it can't move though. Muscles are more repairable than was traditionally thought, and it turns out that nerve fibres can train themselves to adopt different roles: it may well be possible to gift a human being with a functional tail or mobile ears.
This is a gross over-simplification of the immensity of pioneering operations that would be required to turn someone cosmetically into a horse. The process would likely take years with many dangerous operations. The monetary cost would run into at least millions of pounds, and a large medical team comprising several experts in different fields would be required (all of whom would have to be happy with the idea of transforming a human being into an animal - probably the hardest requirement to meet of all!).
Consequently, sadly, we aren't very likely to see equine transformations on the NHS in the near future. But the idea is possible.