Bovine respiratory disease (BRD) has been one of the greatest disease challenges in the cattle industry for many years, but it only acquired this name in the past few decades. According to Dr. Robert Cope, who has been the main large animal veterinarian in Lemhi County, ID, for the past 44 years, cattlemen in earlier years simply called it shipping fever.
“Back in the days when I was in veterinary school, we thought we knew everything there was to know about this disease. We knew it was a complex issue that consisted of three parts that combined to create lung disease: a virus called parainfluenza 3, a bacterium called Pasteurella and stress. In recent years, it became apparent that more factors were involved,” said Cope.
“The list of pathogens now known to contribute to BRD includes several additional bacteria like Mannheimia, Haemophilus and Mycoplasma, plus the viruses infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD), bovine respiratory syncytial virus (BRSV) and probably several others that may not have been identified yet,” he said.
Dr. Andi Lear, clinical instructor of farm animal field services in the College of Veterinary Medicine at the University of Tennessee, said minimizing stress is important, along with a good vaccination program. Vaccination alone won’t do the job, since extreme stress can negatively impact the immune system and leave cattle vulnerable even if they were vaccinated. Stress at the time of vaccination can also hinder the immune system and prevent the animals from mounting a good response to the vaccine.
“We do a lot of cow-calf work here at the university, and we tell our clients that they need some sort of routine herd management,” Lear said. Being able to look at every animal and evaluate body condition when checking the pregnancy status of the cows before going into winter is important, along with evaluating them again before breeding season. Looking at the calf crop also helps producers know if their health and nutrition program is working.
Using appropriate vaccine protocols to prevent BRD, blackleg, etc., in calves is crucial, along with trying to minimize stress as much as possible when working them.
“Take care of the castration, dehorning, pouring for parasites, etc., prior to weaning. We tell producers not to perform these stressful procedures and haul the calves away in a truck on the same day (or even in the next few days). This is one reason there are a lot of sick calves or calves that will soon be sick at a sale barn and why buyers don’t give as much money for them, knowing they are going to get sick,” she said.
“Producers can add value to their product by vaccinating, castrating and weaning prior to shipping to minimize stress and decrease the risk of BRD. It doesn’t take that much extra time but ensures those calves have been exposed to vaccines and have some immunity prior to getting on that truck,” said Lear.
If you do all of this early, while they are still on the cow, it’s not as stressful because mom is there to comfort them after they come out of the chute. “Abrupt weaning on top of vaccinating can be very stressful and can result in a lot more sickness,” she explained.
Vaccination of calves should begin by branding age. Cope generally recommends a modified live virus vaccine containing BVD, IBR, parainfluenza type 3 (PI3) and BRSV at branding, followed by a booster dose before weaning.
“Pasteurella and Mannheimia (Mannheimia was previously known as Pasteurella) vaccine should be given at least at preweaning. Several programs that aid in marketing feeder calves require these vaccinations and can result in higher calf prices at auction,” he said.
“Although several antibiotics (Draxxin, Baytril, Nuflor and others) have been developed that tend to be more effective than some we used routinely in the past, prevention is still far more effective than treatment. Keep in mind, however, that antibiotics are only effective against bacteria, not against viruses,” Cope said.
When considering a vaccination program to prevent respiratory disease, both viral and bacterial diseases must be included. “As previously mentioned, IBR, BVD, PI3 and BRSV are integral parts of the BRD syndrome. When possible, I recommend using modified live vaccine as opposed to killed virus products. There are, however, some instances in which, in the case of BVD, killed products may be preferable.
This can be the case when the cow herd has not been properly immunized earlier, and the calves may be persistently infected with the BVD virus. In that situation, modified live vaccine can actually precipitate the disease. In the case of the other viruses, however, live vaccine is almost always preferable,” he explained.
There are several good intranasal vaccines for IBR and PI3. “These products are given by shooting the vaccine into the nostrils. The advantage of these vaccines lies in how quickly immunity can be gained. Rather than the seven to 10 days that intramuscular vaccines require to produce protective immunity, intranasal vaccine will provide protection in as little as 18 to 36 hours,” said Cope.
“The disadvantage of using intranasal vaccine is simple. There is no intranasal vaccine for BVD, which is one of our greatest concerns,” he said.
Although many calf pneumonias result from bacterial complications of a viral infection, this is not always the case. Sometimes a bacterial infection is the primary and maybe the only pathogen.
“We have found that when the environmental temperature differential between daytime highs and nighttime lows is 40 F or more (such as going from 40 or 50 F at night to 80 or 90 F in the late afternoon), primary bacterial pneumonia—primarily pasteurellosis—becomes fairly common. When this differential exceeds 50 degrees, this pneumonia becomes a major problem.”
Viral vaccines alone will not prevent this primary bacterial pneumonia. “When choosing a Pasteurella vaccine, it is important to know that any effective Pasteurella vaccine must contain two essential components: a capsular antigen and leukotoxoid. Simple Pasteurella bacterins are simply not effective. While there are several good Pasteurella (Mannheimia) vaccines on the market, I have had excellent results with both Presponse and One Shot and tend to recommend either of these,” Cope said.
Dry weather increases risk
Dry weather, smoke and dust put calves at greater risk for respiratory disease. Dr. Eugene Janzen, professor emeritus of production animal health at the University of Calgary, said studies in western Canada in earlier years looked at this problem in cattle on community pastures. “Often they have more trouble on dry years, when conditions are dusty during gathering and working cattle. Dust can irritate the respiratory tract, making the animals more susceptible to problems,” he said. Dust may also carry bacteria with it.
“When calves inhale dust, the first line of defense in the respiratory tract may be overwhelmed. If the inside of the nostrils and upper respiratory tract gets clogged with dust, bacteria are not as readily exposed to nasal secretions, which tend to kill them or help flush them out. If bacteria cling to dust particles, they can be sucked down into the lungs,” said Janzen.
The dust and irritation also inhibit normal action of cilia—the tiny hair-like structures that line the windpipe and move in wave-like motions, continually moving mucus, dust and foreign material up and out of the respiratory tract to be coughed out.
“Shortly after bringing cattle in, if producers had a bad year for dust, they were treating calves for pneumonia,” he explains. Western Canada and many western states have suffered through hot, dry conditions, smoke from catastrophic fires, a lot of dust and stressful weather. In some regions, a combination of hot days (90 F or higher) and cool nights (often down to 40 F) adds additional stress, which hinders the immune system—creating perfect conditions for respiratory disease. — Heather Smith Thomas, WLJ correspondent
