The butter cow was hit early Sunday by Iowans for Animal Liberation, which sent an email to The Des Moines Register claiming responsibility for the vandalism. The group said members gained access by hiding in the Agriculture Building until it closed.
"After dismantling the lock to the refrigerated case housing the Butter Cow with a screwdriver, we doused the entire butter sculpture in red paint," the email said. "The paint represents the blood of 11 billion animals murdered each year in slaughterhouses, egg farms, and dairies."
The vandals also scrawled "Freedom for All" on the glass display window, the newspaper reported.
But a washing has removed the paint, the newspaper said, and security has been upgraded.
"It's sad, because the butter cow is iconic of the Iowa State Fair," Lori Chappell, the fair's marketing director, told the Register. "No one was hurt; no one was injured. The butter cow is fine."
U.S. Sen. Charles Grassley, R-Iowa Republican, saw the butter cow Monday morning, and said it is "emblematic of the greatness of the fair." He said he wanted to deliver a message to the vandals: "Get real."
Animal Liberation Front supporter Jerry Vlasak said the vandalism was a "reminder that there are people opposed to the eating of meat and dairy, and that the meat and dairy industry is inordinately cruel," the Register reported.
Police were reviewing security tips but no arrests had been made.