Highland Horse Haven director Lauren Moses said the haven was established in November last year to rehabilitate neglected and unwanted horses.
Since then, Miss Moses said she had received at least one phone call a day from people asking her to take their horses.
Drought conditions during the summer in Southland and Otago had left many owners unable to feed them.
"We're absolutely inundated now.
We've got space, but not the money to cope with the numbers.
I hate having to turn them down, but their horses won't be in a better place here than they would be where they are now."
Miss Moses said the haven could cope with a maximum of 60 horses and already 52 were being rehabilitated.
With winter fast approaching - the time of year when sick horses came flooding in - she was beginning to worry about how the haven would cope.
The haven operated on funds from the three directors and financial donations from the public.
However, funds were scarce, she said.
The recent drought had left Otago with a chronic shortage of hay.
The haven had managed to buy some from Southland, but it was expensive and not enough to last the entire winter.
Up to 20 bales a day would be needed, she said.
Unless more funds, stock food and volunteers were found, something would have to give.
However, she refused to close the site.
"It's a distressing situation.
We want to help these horses.
Before we came along, the only option for many horse owners was to send their horses to the dog tucker factory in Gore or let them sit and starve in a paddock.
"These horses are good horses and they deserve to be more than something in a dog's bowl.
There's too much demand for what we do.
"But there will come a time soon when we just can't take any more horses."
Miss Moses said it was hoped 15 of the rehabilitated animals on the Mt Cargill Rd site could be sold to raise funds and make way for more.
She also planned to offer riding lessons on site to raise funds for the haven.
