Farmers told Department of Agriculture officials yesterrday that proposed regulations to control speed of the fatal "mad itch" disease among pigs are fine in theory but might not work in the mudhole.

The department has proposed that owners of infected pigs be prevented from selling them to farmers of healthy pigs. But New Jersey farmers at the hearing said it is difficult to tell a healthy pig from one that might come down with "mad itch."

"How can we be assured that infected feeder pigs won't be sold to us?" asked John Villari of the New Jersey Livestock Association.

Under the department's proposals, infected pigs would travel from state to state with permits identifying them as ill and limiting their destinations to a slaughterhouse or a farm with other infected pigs. A spokesman for the USDA said humans cannot contract "mad itch" and that eating pork that comes from sick pigs will not make people ill.

Despite the department's proposals, the farmers said they were worried that they inadvertently would buy infected pigs. "You'll going along according to law and it don't always work that way," Nick Polen told Jerry Peacock of the USDA.

Farmers said blood tests on pigs to determine "mad itch" have not always been reliable. They said a program to kill sick pigs would protect them more than shipping regulations.

Department officials said more technical competence would be necessary before the government could start a program to kill sick pigs, immediately and reimburse farmers for their losses. They said such a program might be begun in about a year.

Pigs that contract "mad itch" - otherwise known as pseudorables - do not have the leisurely pleasure of lolling around. They spend their days rubbing, scratching and licking themselves. They tremble and suffer diarrhea.

Such misery has been caused by a herpes virus that rarely made pigs ill until 1960s. The virus spreads from pig to pig when they breathes on each other or eat food that has been licked by an infected pig.

Older pigs usually suffer until they are brought to the slaughterhouse. Pigs under 3 weeks are less able to cope with the illness and usually die.

Department officials said there has been an alarming increase in the number of cases of "mad itch" in the United States during the past few years. The disease spread to 1,256 herds in 1977, an increase from 1,256 herds in 1977, and increase from 714 in 1976 and 125 in 1974. It has cost farmers between $21 million and $25 million annually. Total yearly income from the pork industry has been $3.1 billion.

Department officials said farmers in the swine belt of the Midwest, where "mad itch" is most prevalent wanted the USDA to issue more lenient regulations than the proposed ones so that they could transport their infected pigs more easily.