By Julie Ingwersen

CHICAGO, Mar 23 (Reuters) - The US pet food industry has no plans to back away from meat and bone meal, a feed ingredient suspected of spreading mad cow disease through Europe but seen as little threat to US pets or livestock.

By contrast, at least three top livestock feed producers have stopped using cattle-based meat and bone meal as a precaution, including number three US feed maker Purina Mills Inc., which dropped the ingredient in January.

Made from ground-up cattle and other types of livestock, and not always separated by species, meat and bone meal (MBM) is an inexpensive source of protein. Experts say as long as the animals used to make MBM are not affected by mad cow disease, the material is perfectly safe in food for cats and dogs.

"If the disease doesn't occur here in cattle, there shouldn't be any danger in pet food," said Dr. Lyle Vogel of the American Veterinary Medical Association.

There has never been a case of mad cow disease, or bovine spongiform encephalopathy (BSE), confirmed in the United States. The brain-wasting disease, believed to be caused by abnormal proteins in the brain and nervous system, is fatal to cattle.

US PET FOOD MAKERS NOT AS CONCERNED AS FEED MILLS

Stephen Payne, a spokesman for the Pet Food Institute, said the MBM produced in the United States remains an excellent source of protein and minerals for pets.

"It's an excellent ingredient. It's highly digestible for dogs and cats," said Payne, whose group represents pet food manufacturers. But individual manufacturers that use MBM were reluctant to comment on the subject.

In Europe, MBM is believed to have transmitted mad cow disease after cattle with the disease were ground up and mixed into rations fed to herds in Britain and on the continent.

In reaction, the US and other nations established laws to keep "byproducts" from slaughter of cud-chewing, ruminant animals like cattle, sheep and goats from being fed back to other ruminants.

Such byproducts are still allowed in feed rations for non-ruminants like hogs and poultry, and in pet food, based on scientific opinion that BSE cannot "jump" into such species.

Still, many scientists think feeding cattle MBM made from sheep carrying the BSE-like disease scrapie was the source of the original outbreak of BSE in Britain in the mid-1980's.

Purina Mills CEO Brad Kerbs said in January that he approved of cattle-based MBM as an ingredient but could not guarantee that the company's large multi-species livestock feed mills would be able to keep it segregated from cattle feed, as required by US law.

Other top ten livestock feed makers shunning cattle-based MBM include Consolidated Nutrition LC of Omaha, Nebraska, and Kent Feeds of Muscatine, Iowa.

MAD CAT DISEASE IN EUROPE

So are Fido and Snowball safe from mad cow disease?

The question remains since BSE belongs to a family of diseases, the transmissible spongiform encephalopathies (TSEs). From studying TSEs, some scientists have linked BSE with related conditions in humans, sheep, deer and mink--and cats.

Since 1990, for example, almost 90 cats--including more than a dozen lions, tigers and other big cats at British zoos--have been diagnosed in Europe with feline spongiform encephalopathy.

No specific pet food has been implicated in the cases, but agriculture officials in Britain said all the cats ate foods that would be expected to contain animal byproducts.

The number of feline cases has fallen sharply in recent years as authorities in Britain and elsewhere have worked to remove contaminated cows from the food and feed chain.

"That epidemic has been over for a while," George Gray, a toxicologist at the Harvard School of Public Health, said of the feline version of mad cow. "It's my understanding there haven't been any cases in a number of years."

FEED MAKERS ADJUST FOR MBM RULES

In the US pet food industry, MBM remains a popular "meaty" ingredient, found most often in dry "kibble" pellets but also in some canned food varieties. Many labels do not specify whether the meat and bone meal came from cattle.

With ruminant byproducts shut out of cattle feed mixes, more MBM may also be showing up in pet food, said Dr. Jean Hofve, a veterinarian with the Animal Protection Institute, an animal advocacy organization based in Sacramento, Calif.

"There was a huge amount of hog byproducts that were going into dog food for a while but now is being routed into ruminant feed. So where is the ruminant (byproduct) going? Well, it's going where the pig stuff used to go"--into pet food, she said.

• More news on Creutzfeldt-Jakob Disease

Related MEDLINEplus Pages:

• Creutzfeldt-Jakob Disease