For producers, it can be downright painful to look into the sick pen and see an animal hurting. It’s a financial hit and maybe even an emotional hardship. One of the few proactive measures available is giving an antibiotic treatment. Then, maybe another treatment the next day if the animal is still not responding.
Today, longer-acting antibiotics are capable of pushing that next treatment further out – up to even 10 days in some cases. With a little patience, producers can treat less and perhaps even return more.
“The duration of action for any antibiotic is dependent on many factors,” says Ron Tessman, DVM, Ph.D., Veterinary Professional Services Manager at Merial. “The intrinsic attributes of the chemical entity itself may lead to the drug having a longer acting effect, such as with macrolides, or it could be due to the formulation.”
Before modern macrolides, the time to retreat animals was defined by two factors: The pharmacodynamics of the product, which show how long the drug stayed in the body of an animal, and the minimum inhibitory concentration (MIC) of the product, which show how long the drug remained at therapeutic levels. Both were straightforward measurements of a product’s duration of activity, Tessman says.
“For instance, with penicillin you had to treat a number of times during the day to keep those concentrations effective,” he says. “A modern macrolide will stay in effective concentrations in the lung to be effective for a number of days.” DSRs, as mandated by Federal law, should always “team” with the veterinarian of record and these veterinarians should be aware of the exact label indications, says Lonty Bryant, DVM, M.Sc., Manager, Beef Cattle Technical Services at Merck Animal Health. The labels for most injectable antibiotics suggest producers treat, then re-evaluate in 24 to 48 hours. There are pharmacokinetic profiles and in vitro susceptibility data for newer macrolides that suggests a longer duration of activity, but the correlation between in vitro susceptibility data and clinical effectiveness is unknown.
The exact response to treatment should be evaluated based on the unique operation, the cattle being treated and the disease risk and other factors, Bryant recommends.
Virtues of Patience
This longer-acting attribute does not always translate into speed, Tessman warns. Treatment of bovine respiratory disease (BRD), for instance, is dependent on pathogens and the health status of the animal. After treatment begins to take effect, the animal must work to regain its nutritional and health status.
“After the stress it has endured, you may not see that animal turn around right away,” he notes. “In a large number of animals, you’re certainly going to see a response, but in some it may take a while to see that response.”
Rather than reaching right away to retreat the animal, it may be beneficial for producers to give the drug more time to be effective, Tessman recommends. This waiting period is known as the “treatment interval” or the time between the one treatment and any subsequent treatments.
“Producers may be able to extend the treatment interval out to 10 days for animals that are on a good plane of nutrition and have good immune status and other things working for them,” he says.
On the other hand, Tessman says that animals under high disease pressure and without good health status prior to the disease challenge may require a quicker retreatment.
“Most people settle between five and seven days for retreatments. That’s what they have found works best in their operations,” he says.
Knowing the cattle’s history and if there is Mycoplasma bovis at work in the herd are two factors that can influence time to retreatment. The bacteria are slower growing than some other disease challenges but can work synergistically with other organisms to cause big problems, Tessman says.
Refrain and Retain
Waiting an extra few days to retreat animals has several benefits for the producer and industry. First, it helps more judiciously use antibiotics overall. Second, it helps save on costs of the intervention, Tessman says.
“There’s always some cost to giving a treatment,” he says. “Bringing animals up to the chute carries a risk of injury or loss because of stress. You alleviate that risk or that unrealized loss by allowing an animal to become more comfortable where they are at and using less antibiotics to achieve the same goal.”
Reduced number of treatments also exposes animals to fewer antibiotics, which helps the industry retain the efficacy of current treatments, Tessman says.
“Producers are aware of this issue from the media attention it has received,” he notes. “But then you have the very real situation of having a sick animal that you really want to do something for. In the end, most people in the industry are concerned about the health of the animals and want to do the right thing. They want to use antibiotics judiciously but don’t want to see them suffering.”
Producers that are truly concerned about purchasing and using less treatment will first start with buying low risk cattle, Bryant says.
“The ability to use less antibiotic should be looked at on a case by case basis and studied diligently to show if we can wait a longer period of time,” Bryant says. “The potential to use less antibiotic is there, but it still comes down to cattle type, management, your employee’s expertise, and what your risk aversion is. If your goal is to have less than one percent death loss, you have to buy them right and manage them right.”
Incorporating New Practices
Training producers to change their traditional practice of pulling and retreating every few days can help them realize the benefits of the longer acting products they’ve invested in, Tessman says.
“The veterinarian has to be out there and training individuals,” he says. “Then, they have to see the effect for themselves to really have confidence in the product. It’s human nature to see suffering and want to do something about that – that’s why I became a veterinarian. I enjoy being around animals and like seeing healthy animals.”
Building a positive history with long acting antibiotics can help reinforce producer confidence that waiting is the right tactic. However, traditional antibiotics still have a place, Tessman says.
“There’s no one-size-fits all approach,” he says. “Some people will start with the cheapest and move their way up to the big guns. Other people – and if you look at most feed yards, this is what they’ve been moving to – will switch antibiotic classes as they recognize animals that are still sick.”
Some producers and veterinarians design their treatment protocols to work down to traditional antibiotics, which are typically cheaper, in order to keep the investment low as the prognosis worsens, Tessman says.
Distributors can help producers and veterinarians find a protocol that works for them. Developing a sound treatment plan can help put DSRs in the role of trusted adviser.
“DSRs can make more long-term gains by recommending the product that is going to work best for a producer and his operation,” Tessman says. “A one-size-fits-all recommendation is just like a one-size-fits-all T-shirt. It doesn’t actually fit everyone. Try to address the needs of the operation and the outcome the producer expects.”
Returning to the product label as a base can help both veterinarians and DSRs cut through any confusion, Bryant recommends. “If they are confused about the coffee shop talk, just read and understand the labels,” he says. “That really cuts through the confusion. Then it boils down to each person’s different decision-making process.”
Key Antibiotic Classes Used in Ruminant Veterinary Medicine:
|Beta Lactams||Penicillins, Cephalosporins|
|Macrolides||Tylosin, Tilmicosin, Tulathromycin, Gamithromycin|