An unusual coalition of farmers, environmentalists and animal-rights defenders asked the Food and Drug Administration yesterday to delay licensing a new genetically engineered growth hormone that could increase dairy cows' production by at least 20 percent in the next few years.

The petitioners asked the FDA to conduct an environmental impact study under the National Environmental Policy Act as a prelude to denying approval of Bovine Growth Hormone (bgH), a product being readied for market by at least three major American companies.

An FDA spokesman, citing a legal ban on disclosure of "trade secrets," would not confirm that any of the firms -- which include the Monsanto Co., American Cyanamid and Elanco -- has applied for approval of bgH. But, the spokesman said, "We are aware that several groups are doing research on bgH in hopes of increasing milk production."

An official of Monsanto, which is developing bgH in combination with Genentech, a California biogenetics firm, and Cornell University in New York, would not comment on the status of the research. He said, however, that Monsanto is "shooting for 1988" as the earliest date for marketing bgH.

Economists at Cornell have predicted that FDA approval of bgH could have a dramatic adverse effect on the dairy industry, which is grappling with massive overproduction and a government program to reduce purchases of surplus milk, butter and cheese that have cost more than $6 billion in the last three years.

The Cornell economists, although acknowledging a probable short-term drop in consumer prices, predicted that quick adoption of the hormone throughout the industry could lead to more surpluses and force 25 or 30 percent of dairy farmers out of business.

BgH, which occurs naturally in dairy cows, can be reproduced in commercial quantities through genetic engineering. The bgH is injected into cows, usually on a daily basis. Almost overnight it could boost production 20 percent or more, the economists said. In the carefully managed Cornell herd, top individual increases were near 40 percent.

"It is legitimate to question whether technological advancements are social progress," said Mike Cannell, a Cazenovia, Wis., dairy farmer representing the Wisconsin Family Farm Defense Fund, one of the groups petitioning the FDA.

"Bovine Growth Hormone is not in the good culturally and socially for the industry on which it will have its impact," Cannell said. "There is one key question: What do we want rural America to look like and what kind of society do we want functioning in rural America?"

Cannell said that he and fellow dairymen fear that widespread adoption of bgH will lead to dramatic production increases, which in turn will drive down prices and force many smaller farmers out of business.

"Demand for milk will not increase," he added, "and we already know that the government under the new price support program will not buy the surpluses. Something will have to give . . . . When 20 percent of the farmers are forced out and another 20 to 25 percent will be impacted and pushed toward going out, who is benefitting from the use of bgH?"

Coincidentally, the Agriculture Department yesterday began the first phase of a surplus reduction program that will cost about $1.8 billion over the next 18 months. The program pays farmers to stop milking their cows and instead send them to slaughter or export markets. About 950,000 dairy animals are expected to be taken out of production.

Other petitioners were the Foundation on Economic Trends and its president, Jeremy Rifkin; the Humane Society of the United States, and Douglas LaFollette, secretary of state in Wisconsin, with support from the Wisconsin Farmers Union and the Farmers Union Milk Marketing Group in the state.

Their petition contended that introduction of bgH will damage the environment by intensifying production pressure on cropland, cause unnecessary suffering to cows because of the physiological stress of increased milk output and cause widespread damage to the dairy economy.

Rifkin said that Wisconsin, with 41,000 farmers the country's leading dairy state, will be the headquarters for a nationwide drive aimed at publicizing the potential impacts of bgH on the dairy industry and on rural communities that rely on milk production.

"Even if the Cornell studies are 50 percent off, we are talking about big changes in the dairy industry," Rifkin said. "This is the first time a constituency adversely affected by the biotechnological revolution has reacted to defend itself . . . . If farmers do not fight back, they are out of business."

"We are giving the FDA 30 days in our petition to carry out the impact studies or we will go to court. We want bgH to be identified with genetic technology. Its introduction will mean a series of Youngstowns all over the Farm Belt."

The petitioners' request to the FDA relied on an impact study by Dr. Robert J. Kalter and other Cornell economists, who predicted serious implications for the dairy industry if the use of bgH became commonplace.