I actually think the livery is repugnant. For someone to post on here their concerns and ask for advice, they are probably stressed, like they said when his companion was PTS, she expected the same for this horse, they see this animal at its worst. They are left with a problem that is not theirs.
To leave a horse which is a flight animal struggling to get up, and therefore unable to get away from danger, is cruel. I have not had to PTS one of my oldies for a couple of years, and I have a couple with dental problems, which live forage based mash. They are seen by the dentist every three to six months, and their weight is monitored, but if I thought at any stage they were losing their mobility it would be time for them to go.
Every one goes on about the rights of horse ownership, but not the responsibilities, and there seems to be a blind spot that when you have paid your rent you can just forget about, you have done your bit, and you can do as you please.
The LO has to persuade the horse owner to get the vet out, has to negotiate with them to do the right thing, the only person not taking responsibility is the HO. This where even if you have just a very casual livery agreement it should be discussed as in a loan agreement what happens at the end of life,( end of life for a horse may be loss of mobility with no chance of recovery) because when you have long term relationship with an older animal and it's not yours there is likely to be conflict.