More than 100 malnourished horses and ponies have been seized from a single property in west Victoria.
RSPCA Victoria and four other Victorian horse rescue organisations carried out the largest-ever rescue mission in the animal welfare organisation's history on Friday, which involved pregnant mares, young foals, stallions and colts which may not survive the month.
"It's the biggest seizure in our 145-year history," RSPCA spokeswoman Sharon Mackenzie told AAP.
The rescue mission comes only two weeks after the RSPCA seized 13 starving horses from the same property.
The RSPCA and the four organisations - The Winged Horse Equine Welfare Inc, Horse Shepherd Equine Sanctuary, Project Hope and Horses at Auction Preview - now face the task of restoring the horses to health, many of which may die in the coming weeks.
Ms Mackenzie said all of the rescued horses will require intensive veterinary care and a careful feeding program if they are to survive.
Many horses are so underweight that their hip bones, spines and ribs are clearly visible.
A majority also appear to have parasites and worms.
This summer has been the worst in RSPCA's long history when it comes to horse welfare reports, with the RSPCA receiving calls daily about the plight of sick horses.
RSPCA Victoria inspector Lisa Calleja says while drought conditions and rising feed costs have contributed to the rise in cases, owners are nonetheless "directly responsible for ensuring that every animal in their care has the food, shelter, water and medical care they need to keep them safe and healthy".
While they may survive, some horses may be so damaged they will never be fully rehabilitated and will have to live out the rest of their lives at a sanctuary or welfare organisations, Ms Calleja said.
