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Preparing to Test for Bovine TB 101

08 September 2008

By Jamie Larson, University of Minnesota Beef Team. It’s back-to-school time and a lesson in preparing to TB test is due.

Reminders never hurt for those who have been through this before, and many producers are gearing up to test herds for the first time since the state’s TB status changed to Modified Accredited last spring.

Minnesota is waiting to hear whether it will be granted Split-State Status by United States Department of Agriculture (USDA). With the approval of Split State Status, a large part of the state will upgrade its classification, and a smaller section of northwestern Minnesota will remain at the Modified Accredited (MA) classification. Herds in the MA Zone will still be subject to the more stringent shipping and testing restrictions, but other parts of the state will be spared from these extra restrictions if approved.

TB Testing Terminology

The first test that will be performed by a veterinarian is the caudal-fold tuberculin (CFT) test. The veterinarian must be certified by the state of Minnesota to administer and read TB tests. The veterinarian will inject tuberculin in the caudal area just underneath the base of the tail, and then will return in three days to “read” the test, which involves examining the injection site for any swelling or discolorations.

If a reaction to the injection is present, the animal is considered a “responder” or “suspect” and will go through a second round of testing. It can be expected that 2 to 7 percent of any given herd will be found to be “responders.” If your herd has any suspect cattle, the whole herd will be quarantined until the animal is determined to be negative on the second TB test.

The second test, performed only on the responders, is the comparative cervical tuberculin test (CCT). This test must be performed between 10 and 60 days from the CFT test, and must be administered by a state or federal veterinarian. The vet will shave two areas on the neck area and measure the skin thickness before injections are given to establish a starting base point. Two different tuberculins are injected in the shaved areas. The vet will return three days later to read the tests.

Depending on the skin reaction, cattle can be classified as “negative,” “suspect” or “reactor.” All cattle classified as suspect or reactor are slaughtered, and samples are taken for further analysis to determine if bovine TB is present. If animals in the herd are classified as suspect or reactor to the second test, the whole herd is quarantined until the lab results are finalized. This can take several weeks.

Scheduling TB Tests

Why are you testing? If you will be shipping or selling cattle across state lines, there are federal regulations that must be met. In addition, each state may have its own regulations that may be more stringent, and these need to be followed along with federal regulations. Contact your veterinarian or the receiving state’s animal health agency for individual state requirements prior to moving any animals.

Federal regulations include the stipulation that all feeder cattle must have a negative individual TB test within 60 days of shipment. In addition, sexually intact feeder cattle must also have a negative whole-herd TB test (all animals 12 months or older) within 12 months of movement. Breeding cattle must have a negative whole-herd test within 12 months and an individual negative test within 60 days of shipment. Animals moving directly to an approved slaughter facility (state or federally inspected) have no federal restrictions.

Producers should schedule the initial CFT early enough to allow time for a CCT, if needed. Veterinarians are very busy this time of year, so begin scheduling appointments early and work with them to determine the appropriate time to test.

Many producers want to maximize efficiency and ask what other procedures can be done at the time of testing to reduce the number of times cattle must be handled. In many situations, the attending veterinarian can decide and may charge accordingly if the procedure takes extra time.

It should be noted that stress can increase the incident of false positive results. For example, cattle that are significantly stressed may have more “responders” to the CFT than cattle that are not stressed. Cattle should be handled in a low-stress manor and any procedure that adds stress should not be done at the time of initial injection for TB testing.

To avoid false positive tests, it is recommended that no “extras” are added when the initial tuberculin injection is given. Extra procedures may be added when the veterinarian returns to read the tests if these procedures can be done quickly and efficiently. Extras may include vaccinations, parasite controls and the like. It is not recommended that cattle are artificially inseminated or calves are weaned around the time of TB testing.

If a state or federal veterinarian is performing the test, no extra procedures may be performed at the time of injection. Your veterinarian can answer more specific questions on this topic. While efficiency should be maximized, it is imperative to get accurate results on tuberculosis tests.

TB Tax Credit

Your final assignment is to take advantage of the TB tax credit the state of Minnesota allows. This credit is available for all cattle owners and allows one-half of all expenses to be credited. Allowable expenses are veterinarian fees, including call charges and injection costs, extra labor expenses and expenses related to rental of equipment that the owner would not have otherwise incurred.

Testing must be done by a certified veterinarian and costs must be incurred by Dec. 31, 2008, to be claimed on 2008 tax returns. Work with your tax preparer to get the highest credit allowed. This tax credit was designed to decrease the financial burden of testing placed on producers in the state, so be sure to claim it.

Further questions can be answered by calling the Minnesota Bovine TB Hotline at 1-877-MN TB FREE or visiting www.mntbfree.com. In addition, the University of Minnesota Beef Industry website has educational information on bovine TB, as well as other beef production information and news, at www.extension.umn.edu/Beef.

Good luck on TB testing, and class dismissed!

August 2008

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