The agency says it's rescued more animals this year than it has in the last 20, and it's running out of room to house them all at its center in Fresno.
The SPCA says it is housing 12 horses at its center in Fresno, the most it's ever cared for at one time. 13 others are at nearby foster stables.
It says volunteers worked through the holiday weekend taking measurements to expand the space after more malnourished horses were discovered near Riverdale.
On Friday the Fresno County Sheriff's Office seized 15 horses from a ranch near Riverdale after a neighbor alerted authorities to four horse carcases on the property.
"We sent patrol deputies to assist SPCA and were able to determine there were a number of horses in this field that were not being cared for, they were in various states of dehydration and malnutrition," Lt. Phil Caporale of the Fresno County Sheriff's Office said.
Two of the animals had to be euthanized, one because it had a broken ankle that was left untreated and the other because it was severely malnourished.
Caporale says the farm's owner is out of the country but could face animal cruelty charges.
"At this time we're not able to talk with him to find out what the arrangement was for the caring of the animals," Caporale said.
But neighbors have their own ideas.
Rudy Garcia believes the owner got in over his head. He says a man used to pay him about $300 to put water out for the horses, but stopped several months ago.
"They didn't want to pay because it was too much on the water bill, so we ended up cutting it off," Garcia said.
Another neighbor who didn't want to be identified says the owner sometimes relied on growing grass to feed the horses, but because of little rainfall the animals had very little to graze on.
"They need water, they need food, it's a shame they were left to perish here on the land," the neighbor said.
One of the horses was taken to the SPCA in Fresno. The others will be cared for at the ranch while the SPCA works to find temporary housing for them.
In the meantime, this was the second call authorities responded to in less than a week.
Last Tuesday, a Fresno man was arrested for animal abuse after authorities discovered 19 starving horses on his leased-land near Clovis.
Because of the large number of animals the SPCA has recently taken in it's looking to expand it's facilities.
Right now it's trying to raise $11 thousand dollars to build an arena with additional corral fencing.
So far it says it's raised about half of that.