TB Tests and Ear Piercing

            After weeks of reading about TB testing, we went to see how it actually all occurs.  I mentioned on Day One that TB work is complicated, and testing for TB keeps with the trend.  It couldn’t be a simple blood draw, look under a microscope and give a definitive “positive” or “negative”: instead, we drive to a farm on day one and intradermally inject Tuberculin into the caudal fold and come back 72 +/- 6 hours later to see if there was any rejection at the injection site.  A reaction usually means a swelling at the site.  If there isn’t any reaction, the animal is negative and good to go.  Unfortunately, the test is not perfect so 3-10% of negative animals will react regardless. This sounds small but on a 1200 head dairy that can mean 120 animals.  Any animals that react to the Caudal Fold Test are classified as “Suspect” and we do a secondary test which is either a gamma interferon test (blood test) or a Comparative Cervical Test (another intradermal injection which means coming back another 3 days later).

Dr. Schwarck injecting Tuberculin into the caudal fold

            Today we injected two herds both pretty small- 8 at the first, 25 at the second.  I quickly discovered that the hardest and most important part of the whole testing process is setting up the gates.  Many farms do not have their own equipment, so State of Michigan field vets haul in their own chutes and gates.  The idea is to set them up so that there is always a gate between you and the animals—safety first!

Setting up gates and the chute

          At both farms, Danielle and I got to practice putting in RFID (Radio Frequency Identification) tags so they can be tracked electronically wherever they travel in Michigan.  It is an eerily similar process to getting one’s ear pierced.  The gun is loaded with a tag (earring), it is placed somewhere along the ear, and then it’s clamped down to poke through the ear and lock the tag into place.  Now I know I was told when I got my ears pierced that it wouldn’t hurt, but those people lied, so I sure didn’t blame the cows when they threw their heads around in protest.  Unlike my earrings though, these tags are tamper-proof and will ideally never be removed or changed in the lifetime of the cow.  Any cow with an RFID tag has an individual number on that tag that reads something like 84003005555555.  This number can be scanned with a wand and it will show up in the USAHERDs database with a record of where the animal moved throughout its lifetime and its TB test results.

Ear Tagging