John A. Hoyt, a Presbyterian minister who left the church to advocate for animal welfare as president and chief executive of the Humane Society of the United States, died April 15 at his home in Fredericksburg. He was 80.

He had progressive supranuclear palsy, a rare brain disorder, said his daughter Peggy Hoyt.

Mr. Hoyt joined the Humane Society of the United States in 1970 as its president. During the next 27 years, he helped grow the organization from a rented office with a few employees to an international operation with headquarters in Washington. The society, founded in 1954, is one of the largest animal welfare groups in the country.

In an interview, his daughter said he approached his work promoting the welfare of animals as that of a minister tending his flock. He campaigned against dog racing, horse racing and rodeos, calling the popular entertainment spectacles of animal abuse. He called for the end of whaling, fur trading and the clubbing of baby seals.

“When they are hunted and captured and caged and slaughtered for frivolous items to merchandize, do we not feel their pain and suffering?” Mr. Hoyt said in an animal welfare film. “Do we not feel some sense of shame that we as a society have become the executioners of so many others?”

John A. Hoyt, president and chief executive of the Humane Society of the United States, died April 15. (The Humane Society of the United States)

Mr. Hoyt successfully lobbied Congress to pass animal rights legislation and also developed effective public awareness campaigns, Colorado State University animal welfare expert Bernard Rollin said.

In the early 1970s, Mr. Hoyt ordered an undercover investigation of more than 70 public and private zoos in the United States.

The report found that in a number of menageries across the country, animals were routinely mistreated, including chimpanzees chained to their cages, dehydrated animals with no water supply and elephants dangerously packed into small enclosures.

Rollin said that during the mid-1980s, Mr. Hoyt was a crucial supporter of legislation to improve the treatment of laboratory animals such as rats and mice.

“It was a big deviation from traditional humane society concerns of cats and dogs,” Rollin said. “Hoyt put the power of the Humane Society of the United States behind the legislation, which signaled the beginning of a larger movement concerning non-pet animals.”

Mr. Hoyt also started a children’s education program to promote the humane treatment of animals.

John Arthur Hoyt was born March 30, 1932, in Marietta, Ohio. His father was a Baptist minister. He was a graduate of what is now the University of Rio Grande in Ohio and received a master’s degree in divinity in 1957 from what is now Colgate Rochester Crozer Divinity School in Rochester, N.Y.

He served as a Baptist minister before joining the Presbyterian church. He was serving as a senior minister of the First Presbyterian Church in Fort Wayne, Ind., before joining the Humane Society after a college friend recruited him to the organization.

He said his work with animals was partly inspired by his grandmother, a vegetarian who kept 40 pet sheep and named each one. Mr. Hoyt always kept dogs and cats in his home.

Survivors include his wife of 54 years, Getrude Mohnkern Hoyt of Fredericksburg; four daughters, Peggy Hoyt of Chuluota, Fla., Karen Willcox of Frederick, Anne Williams of Sperryville, Va., and Julie Dorman of Boyds; a brother; four sisters; and five grandchildren.

In 1982, a 650-pound vegetarian bear that ate Twinkies was a featured guest at the D.C. Armory’s recreational vehicle show. The bear, Victor Jr., stood 7 feet 2 inches on his hind feet and wrestled with willing contestants.

In an official letter of protest to then-D.C. Mayor Marion Barry, Mr. Hoyt wrote that “for the sake of the bear and the safety of the public we call on you . . . to bring a halt to this exploitative and cruel ‘entertainment.’ ”

Not long after, the bear act left town.