"It looks like hell. I don't know how else to describe it," said Maleah Stringer, director of the non-profit Animal Protection League in Anderson. "Bodies are piled up on top of each other. The alive ones are sleeping on the dead ones. It's horrible. It's horrific."
WISH-TV, Indianapolis, reported county Sheriff Ron Richardson called it "a very serious situation."
"In my career, in over 35 years, I have never seen anything this large," he told reporters Wednesday.
The animals found Tuesday in the Madison County barn included chickens, cows, geese, sheep, goats and horses, The Indianapolis Star reported.
The TV station said 30 animals were found alive but thirsty, including eight mini horses, six sheep, a llama, two ponies and some chickens, ducks, turkeys and rabbits.
Police, veterinary officials and prosecutors were investigating the animals' deaths.
Stringer said her group would find foster homes for the remaining animals after veterinarians examine them. Richardson said he didn't know if any animals would need to be euthanized.
Property owner Daniel Ault, who owns a meat-processing business in Grant County, was not at the property when officials first arrived, WISH said.