The destruction brought to a sad close the efforts of the SPCA, the International League for the Protection of Horses (ILPH) and experienced standardbred owners to save the unhandled animals.
Sadly, the most emaciated of the the two mares originally rescued from the property was also put down at the SPCA headquarters in Westney Road, Mangere, leaving a foal without its mum. The decision was made that the animal's condition was too poor for it to continue.
A mare and foal from the South Auckland property.
ILPH welfare officer Sandra Shearer was at the 10ha (25 acre) property on Thursday morning.
"It really was a relief to see them go," she said. "It's really, really, sad."
She said it was a shame the elderly and ill owner had not put his hand up for help earlier.
Ms Shearer had been part of the unsuccessful effort on Tuesday remove the horses. In the end, just three were successfully caught and left for a new home with an experienced horse handler.
She emphasised that a huge effort had gone into trying to catch the horses, which were in three mobs with a stallion in charge of each.
SPCA inspector Vicki Border said on Wednesday: "They are better off being euthanized. I don't think it's necessary to put them through any more stress. They are better off in heaven."
"It's a hard decision, but I have made it in consultation with the vet."
The horses, she said, had experienced little human contact. "The only human contact was a bit of hay over the fence. They have not even been out of the paddocks they have been in."
She said she realised some people would voice disapproval of the decision, but she was satisfied it was the right decision. "I stand firmly by that decision," she said. "These calls have to be made."