In 2000, Dr. Peggy Hsieh’s (Professor & Researcher, Florida State University) research brought to market a commercial test to aid regulators in enforcing a new ban on ruminant meat bone meal in cattle feed. Now Hsieh says her new research will bring to market a commercial test to enforce a 2009 ban on ruminant central nervous system tissue in cattle feed.

Progressive Dairyman Editor Walt Cooley spoke with Hsieh about her research. He also spoke separately with the feed industry about how it feels the new test may impact the enforcement of feed regulations.

How does the test work?

HSIEH: This is a rapid new test. It uses a newly developed antibody as the probe. Because this antibody is specific to the bovine central nervous system, it only recognizes a marker protein of central nervous system tissue.

This test will be able to rapidly and sensitively tell if there is any bovine central nervous system tissue present in any food or feed materials regardless of whether the material is raw or processed.

Why is such a test necessary?

HSIEH: In the U.S., the FDA has banned ruminant meat bone meal from animal feed since 1997. The FDA banned ruminant central nervous system tissue from human food in 2004 and more recently in 2009 banned it from animal feed.

According to the USDA, the most important safeguard against BSE is the removal of specified risk materials, such as ruminant central nervous system tissue, from the human and animal food supply because it harbors the highest infective agent in infected animals.

So why do we need this test kit? The problem is feed contamination, from the slaughtering room or the rendering facilities, and the mislabeling of feedstuffs. This occurs frequently and is seen as a major concern.

The FDA has issued many costly animal feed recalls simply because of potential contamination or mislabeling. Therefore, we needed some kind of a user-friendly and a reliable assay. This assay will mainly be available for regulatory enforcement to protect our food supply and the health of animals.

How is this test different from tests currently available?

HSIEH: Currently there is a commercial test kit available to detect central nervous system material, but it only works in raw, unprocessed meat or feed materials. That’s because the current test’s marker protein is a different native protein, one that is not heat-stable.

Our test’s marker protein, called the myelin basic protein, is a major protein in the bovine brain and also in the spinal cord. Our test uses antibodies to detect the presence of this marker protein based on the binding of the antibody on the heat-stable region of the marker protein.

Also, another difference between our kit and the only commercially available kit is that ours is ruminant-specific. Only ruminant animals’ central nervous systems harbor the highest concentrations of the BSE prion, the infective agent of the disease.

For this reason, international laws prevent the use of any ruminant central nervous system tissue (the brain and spinal cord), or the major specified risk material, in human food or animal feed. Therefore, any test’s ruminant specificity is very important. Those are the two major differences between our test and the other test.

How specific is the test? Does the test ignore other bovine proteins?

HSIEH: This test uses a ruminant-specific antibody. It only recognizes the marker protein of the ruminant central nervous system tissue and differentiates from the central nervous system tissue of other animals. As you said, it ignores other bovine proteins.

We have evaluated our new test on peripheral nervous tissues, which are not risk materials. It does not recognize them. It only picks up the central nervous system tissues, and only those from ruminant species, the ones prohibited from food and feed. In other words, it’s very specific.

How sensitive is the test?

HSIEH: According to our experiments, sensitivity is very low, below 1 percent; I think that it’s .05 percent by weight. That means it can detect in a sample of meat or feed any brain or spinal tissue that is at least .05 percent the weight of the total sample.

How long will it take for a commercial test based on your research to be available?

HSIEH: Usually it takes at least six months or maybe one to two years. Our research has been done for about three years, and the company is about ready to put the assay on the market after confirming that the commercial test is shelf-stable.

What implications do you believe a commercial test might have for the feed and food industries?

HSIEH: First, this will avoid many feed recalls and the huge economic loss associated with those recalls that are due to false positive results. In the past, it has happened often.

So, I think with this more effective kit it would be very beneficial to the rendering and feed industry. Beef processing plants, meat dealers, feed vendors, farmers and other researchers could also use it to enforce labeling laws and ensure food and feed safety.

The feed industry’s concerns are that there could potentially be more recalls if the test is hypersensitive. Do you think their concerns are valid?

HSIEH: This is exactly the problem. Before this point in time, there was no effective test available. If feed manufacturers really wanted to test for ruminant central nervous system material, they had to use a DNA test; however, a DNA test is prone to contamination.

It may produce false-positive results. DNA is also universal; it cannot differentiate prohibited feed material from allowed material. It could only differentiate material between species.

The feed industry’s perspective
Richard Sellers of the American Feed Industry Association says that 99 percent of FDA inspections of feed manufacturers’ facilities are compliant with current BSE-related feed regulations. This new test is “bone-shaking,” he says.

“We don’t know what an infectious dose of BSE prions is. We will have to rely on FDA to determine that,” Sellers says. “If we have a test that finds a minute amount of central nervous material from a bovine in feed, are we supposed to ban the feed and recall it? If you look at the FDA’s current rule, they expect a certain amount of carryover.”

Carryover is a negligible amount of a substance that could exist as a residue even after cleaning. Sellers says feed manufacturers currently physically clean out or flush their mills between batches of restricted ingredients.

FDA says these processes are valid methods for removing restricted ingredient residues. Sellers is concerned how the new test may influence FDA’s expectations of carryover for feed mills.

“You can never perfectly clean out a feed mill, a rail car or a bin,” Sellers says. “If this test is specific enough, you may find some nervous system material. But the question is: What does it mean? Is all nervous system material wicked and bad and should be banned?”

Sellers says that if the FDA were to approve the test for regulatory purposes it may redefine acceptable levels of carryover, which have previously been defined only by adherence to the cleaning methods used to avoid them.

“The bottom line is that even with this test, the FDA will need to do a records check,” Sellers says.

“The rule bans use of all ruminant protein in feed, not just nervous tissue. A rule change would likely be needed to make this the compliance option of choice. However, it could be another tool for feed mills.” PD