Not sure why the application of OMT to horses should strike folks as strange, anymore than the use of drugs or surgery in veterinary practice.
The chiros have postgraduate courses in the use of manipulative therapy on animals other than humans, with some co-operating with Vets regularly.
And I trust that the note that British osteopaths are not physicians isn't taken to mean that they are less than professional - whether they're treating humans or other beasts.
I suppose it's a case of horses for courses!
(Ha! Sorry, couldn't resist.)