Senior animal protection officer Kent Kokoska said when officers discovered the four horses over the course of the past month, they were basically skin and bones.
"Of the emaciated horses in our care, we had one horse that we were unable to remove to veterinary care, so we had to euthanize it," said Kokoska. "That speaks to the degree of suffering the animal was in."
Kokoska said the locations from which the horses were seized are within a one- or two-hour drive from Kamloops. He said members of the public passing by would have been able to see the emaciated horses — which makes it disturbing no one called the SPCA sooner.
He says the horses clearly faced longstanding neglect that wore them down to the point they could barely stand.
"Usually we start getting these calls in early spring, when animals or horses have had a tough winter," said Kokoska.
"Going into winter, this is really unacceptable... So we're just putting out the plea that this is not acceptable, it's not normal, people should be calling."
No charges have yet been laid but animal cruelty investigators are gathering evidence.
If convicted of cruelty to animals, owners could face fines of up to $75,000, up to two years in jail, or both.