One of the nation's largest meat processors pleaded guilty in federal court here yesterday to shipping hams contaminated with mouse droppings to the Walter Reed Army Hospital.

The shipment was made from Swift and Co.'s distribution center at 1431 Okie St. NE here nine months after the company's own sanitary inspectors had found serious rodent problems at the same plant, it was stipulated in court.

Although Assistant U.S. Attorney Albert H. Turkus, of the fraud division, asked that the company be penalized by a "substantial fine" of up to $10,000 for the felony plea. U.S. District Judge Aubrey E. Robinson Jr. instead sentenced the firm to pay a $500 fine for the illegal shipment.

Attorneys for the meat company said the firm "deeply regrets . . . that a breakdown on rodent control" occurred at the plant, but that it had been corrected after the contaminated hams were discovered.

According to the charge, mouse droppings were found in two cardboard boxes that had been shipped to the Walter Reed Army Medical Center in November, 1975. In the boxes were 111 pounds of frozen hams.

Prosecutor Turkus said in court that Agriculture Department investigators took samples of other meant in the same shipment and found a "great deal of evidence of the rodent infestation."

Agriculture Department inspectors then referred the case to the U.S. Attorney's Office here for prosecution. A subsequent grand jury investigation turned up internal Swift memos dated in February, 1975, concerning serious rodent problems at the Okie Street location.

Although the company took some action, according to internal documents, another investigation in June, 1975, showed a rodent problem still existed there.

In asking for a substantial fine, Turkus said the government did not decide "lightly" to file criminal charges against the company. "But they (Swift) knew of the problem, and clearly did not make a substantial effort" to rectify it, Turkus said.

In a statement to the judge, Swift's attorneys said the rodent problem at the facility was caused by the bad condition of buildings in the area where it is located, as well as the presence of open fields in the area.

The company regularly inspects its 300 facilities and views sanitary problems with "utmost seriousness," the company's attorneys added.

"It is hoped that Swift's long history of providing quality meat products, and the satisfactory corrective action taken by the company at its District of Columbia facility will be considered by this court in imposing sentence," the attorney said.