Washington, D.C. - The U.S. Food and Drug Administration is slated to release on Thursday guidelines for genetic engineering of animals for food, drugs or medical purposes.

The guidelines, long overdue and the result of years of discussion, could open the door for the commercial production and sale of rapid-growing fish, environment-friendly swine, cattle resistant to mad cow disease and animals with meat that have healthier contents.

A small number of biotechnology companies and scientists have already bred genetically modified animals but the lack of clear regulatory guidelines prevents businesses from investing in the area.

The FDA conference call, confirmed by FDA spokeswoman Judy Leon, is expected to pronounce that genetically engineered animals will be regulated by the same laws used on animal drugs. Stricter regulation on genetically modified animals is expected compared to cloned animals which have no added genes. Last year the FDA had ruled that meat and milk from cloned animals are safe for consumption and would require almost no regulation.

For genetically engineered animals, each type of modified specie would need a separate approval from the FDA, which will test the effect of the animal meat or milk on human health, animal health and the environment.

Biotechnology firms are happy with the issue of the guidelines. Barbara Glenn, managing director of animal biotechnology for the Biotechnology Industry Organization, told the New York Times, "We feel this will enhance investor confidence in this technology... A strong regulatory process translates ultimately into public confidence."

Critics wait for the guidelines to be published. A skeptical Margaret Mellon of the Union of Concerned Scientists told Washington Post, "The first time that the public will learn about a genetically engineered animal will be the first day it is approved... This requires that you completely trust the FDA to do this right, and I don't think folks trust FDA that much."