The South Florida SPCA reckons Freedom's Flight would be perfect for the role.
The backers of the movie have been seeking several horses to play the role of the Triple Crown winner.
Secretariat is Freedom's Flight's great-great-great grandfather.
The South Florida branch believes casting the horse would send a great message on behalf of rescued horses everywhere.
It wrote to the producers, urging them to consider the application of Freedom's Flight, now owned by Richard "Kudo" Couto.
"Freedom's is a big, flashy chestnut, is a fourth generation descendant of Secretariat and resembles him greatly," the branch wrote to the producers.
"But more important, Freedom's was rescued by from a Miami slaughter ranch when he was within just a few hours from being illegally butchered for his meat.
"Freedom's has become a world-wide celebrity in his own right as his 'dad', Richard "Kudo" Couto, has spearheaded the efforts to tell the world about illegal horse slaughter in the United States and abroad.
"Freedom's story has been featured as far away as Russia (Pravda), Great Britain, New Zealand, etc."
The branch said the horse is spirited and temperamentally sound.
"He is used to cameras and loves people. He is very used to photo shoots and retakes. He loves the attention. Physically he is not 100% sound. In his fourth start, he broke his leg out of the gate at Gulfstream Park. He still managed to finish third. n fact, he placed in all four of his starts.
"Three months later he was on the slaughter farm. Freedom's is light rideable, capable, very courageous and easy to handle.
"Just think what a public relations and promotional bonanza Freedom's backstory would be if he were in your movie.
"As you know, too often Disney animal movies result in people rushing to buy pets leading to overpopulation and abuse. For instance, 101 Dalmations. It would be a great public service if Freedom's backstory were part of the promotion for the Secretariat movie."
The branch urged people to contact email@example.com to convince Disney producers to use Freedom's Flight.