The government moved yesterday to halt the sale of more than 70,000 cattle known to have been implanted illegally with the banned growth stimulant DES, which causes cancer in laboratory animals.

As many as 200,000 steers, or about two-days' normal slaughter, may be affected in five states, primarily in Kansas and the Texas Panhandle, according to a joint statement from the U.S. Department of Agriculture and the Food and Drug Administration.

Some cattle illegally fattened with the aid of DES "unquestionably" already have been sold, slaughtered and consumed, according to Tom Grumbly of USDA's Food, Safety and Quality Service. However, he said, the meat is "no worse than any that was on the market prior to the ban," which went into effect last Nov. 1.

DES, or diethylstilbestrol, is a synthetic estrogen that was prescribed a generation ago to control human pregnancy disorders. however, some daughters of the treated women developedvaginal or cervical cancer and some sons suffered genital abnormalities. Laboratory animals developed cancer when fed DES, which has been used nationwide since 1954 to speed cattle fatteniing.

Livestock and feed industries and DES suppliers fought proposed bans for seven years and have challenged the most recent one in court. "An investigation by FDA over the past two weeks has revealed widespread disregard for the ban," the two agency heads said in the joint statement.

"These violations simply are not acceptable. A drug associated with a long-term health hazard has been deliberately introduced into the food system in violation of the law."

Grumbly said two officials of Allied Mills Inc., a Chicago-based subsidiary of Continental Grain Co., voluntarily disclosed to the FDA last March 14 that DES was being used at two Allied feedlots in Kansas.

FDA investigators found that the DES pellets, which are implanted behind animals' ears, has been distributed by Walco International Inc., of Porterville, Calif., and Schmidt-allen of Greeley, Colo., after the July 13 cutoff date for sales. The two firms are voluntarily recalling any existing stocks, the agencies said.

The pellets were then implanted in steers after the Nov. 1 deadline in 30 feedlots, the statement said. Fifteen of those were in Kansas, eight in Texas, four in Colorado, two in California and one in Nebraska. In letters sent out yesterday, the feedlot owners were ordered to remove all the implants and hold the cattle until the DES has been eliminated from their systems.

That means the affected animals will be held for at least 35 days, 63 days if the kidneys or livers are to be used for human food.

The National Cattlemen's Association immediately protested that the time requirement was "impractical and will needlessly delay the marketing of cattle."

While noting that the organization "does not condone in any way the use of any product which has been ruled illegal," spokesman Roger Berglund said a delay of 120 days after the pellet implantation had been the norm before the ban and ought to be used now.

That period, he said, was sufficient previously to guarantee elimination of DES. "There never have been any DES residues in edible tissue as a result of commercial use of DES implants," he said. "There is no cause for concern about the wholesomeness and safety of beef."