Can Metaphylaxis Use be Reduced by Technology?
BY BRUCE DERKSEN
While metaphylaxis treatments have been a staple of most feedlots, society’s pressure to reduce the use of antibiotics is real and ever increasing. In response, operators are constantly attempting to find and access methods of identifying bovine respiratory disease (BRD) susceptible calves, without needlessly treating those that would have otherwise stayed healthy. To conscientious owners, this of course makes financial and environmental sense.
Jenna Funk, DVM and Associate Veterinarian with Metzger Veterinary Services, Linwood, Ontario, and recent Iowa State University researcher, covered her Master’s Degree on the diagnostics for BRD and has seen much of the research behind technologies in use or being developed for this field.
Practical Considerations First
She says before specific technologies are used, there are practicalities feedlot operators can look for in arriving calves. Main factors considered are age, weight, place of origin and gender.
Intact bulls are also a big concern. “If calves have to be castrated at the feedyard that’s an incredibly stressful event opening them up to getting sick because their immune systems are down.” Heifers also seem to be slightly more susceptible to BRD than steers, and lighter calves from multiple origins are more likely to become ill than heavier calves. “The poster child of being open to BRD is a lightweight calf run through a sale barn and mingled in a nose-to-nose situation with God knows how many animals. Light weights that maybe haven’t been vaccinated and were just pulled off their Moms. Those are the ones we worry about most.”
Detection and Confirmatory Categories
Funk says technologies for diagnosing BRD are split into detection and confirmatory categories. “Detection tests occur in the home pen to find the sick animal, and the confirmatory test is done chute side on an animal identified as maybe being sick. That test is to determine whether an animal truly has BRD.”
She describes the most common combination of detection and confirmatory tests for clinical evaluation as typical pen riding. But even with proficient riders, numerous trials demonstrate this appraisal isn’t good enough, with average numbers indicating approximately 60 percent of BRD cases are caught in the pens.
“Pen riders are generally good at what they do, but these are prey animals doing everything they can to hide sickness,” she said. “It’s a poor measuring stick, but it’s the one we have and the one everything is compared to. When we start looking at these tests, we have to remember we’re coming up against a bit of an odd standard.”
Targeting the Pen
For technologies targeting the pen, Funk says the big one is feed intake. Companies such as GrowSafe and Zoetis have developed electronic feed intake monitoring systems that recognize how many times a calf goes to the bunk, how long it spends there and how much it eats. “We know, just like sick people, sick cattle eat less. It’s usually a sign they’re not well.”
Both these technologies create computerized algorithms from gathered information to flag sick animals. “It’s still fairly expensive to implement the technology. You’re looking at a decent start up cost to get it in the feedyard plus the tags that go into every animal.”
Rumen boluses are also a pen technology in use. Inserted into the animals on arrival, they monitor everything from temperature to rumination. Some determine how much animals are moving about the pen. Information is used to create algorithms calculating fluctuations in temperature and rumination, plus screen for rumen PH levels. “Again, these are fairly expensive to initially implement,” said Funk. “Startup costs include boluses as well as computer systems and receivers placed around the pen.”
Aiming Chute Side
A second group of technologies target confirmations chute side. “Part of this puzzle is rectal temperature is a poor indicator of BRD. Many things cause fever in animals with BRD being only one. Confirmatory tests try to link their results to treatment outcome—can we predict if the animal is going to get better or not based on this test?”
Lung ultrasounds represent this category, scanning lung surface to determine damage. Funk says this procedure works better in younger and lighter animals, as the portion of the lung required for scanning becomes hidden beneath the front shoulder as cattle grow. For this reason, feedlot use is generally limited.
The Whisper stethoscope created by veterinarians in Western Kansas and presently owned by Merck Animal Health, is another promising chute side technology. In the original model, eight second lung sound recordings were made and wirelessly transferred to a computer where they were analyzed and electronically scored on a scale from 1 to 5—healthy to chronically damaged by pneumonias. Later, this Whisper system became focused for treatment use rather than on incoming calves.
Merck then pursued the technology further, again targeting arrival animals, eventually constructing an entirely different Whisper program with a new stethoscope and algorithms aimed at listening to the lungs of inbound calves.
Other Specialized Testing and Benefits
Funk says other random technologies analyze serums, blood samples and nasal secretions, attempting to uncover changes in the blood associated with BRD by using equipment such as mass spectrometers. “We know there is some difference in blood and nasal secretions between sick and healthy calves. Research is being done but has a way to go before it’s really chute side applicable.”
She believes benefits beyond the simple reduction of antibiotic use include lower cost inputs and fewer injections, lowering the risks of reactions and site lesions.
“Obviously, the reduction of antibiotic use has many effects. Reducing our chances of creating multidrug resistant microbes is the big push.”
Society’s pressure to reduce antibiotics is likely to continue and increase. “As it stands now, we have no gold standard for diagnosis of BRD,” said Funk. “We have no single test that promises a hundred percent ‘Yes’ this animal has BRD or ‘No’ it does not.” She cautions results are not instant but is encouraged by the work of researchers pursuing detection and confirmatory testing in combination with advancing pen and chute side technologies.