Respiratory disease is the most common cause of death of feedlot cattle, and a great deal of the research has been focused on it at this stage of production.

However, BRD is also the most common cause of death for nursing beef calves older than three weeks, and much less is known about the syndrome in this age class.

However, like the disease we see in feedlot calves, we know that BRD in pre-weaned calves can occur because of exposure to a variety of viruses and bacteria as well as many risk factors such as immunity, insecurity issues and stress.

LISTEN: Preventing BRD on cow-calf operations

In the most recent edition of the Canadian Veterinary Journal, Dr. Nathan Erickson and colleagues published a clinical trial that focuses on one aspect of the neonatal vaccination question in beef calves — specifically, does vaccination with a bovine coronavirus vaccine prevent respiratory disease in a commercial cow-calf herd with a history of BRD treatments in young calves?

Bovine coronavirus has been suspected as a virus that may be involved in some of these BRD outbreaks, and this trial examines whether some of the current commercial vaccines can reduce the number of calves that need to be treated.

The trial

Erickson and his team performed the trial on 887 mixed-breed calves born from Feb 16 to May 28 at a commercial ranch in Alberta.

This ranch had a history of previous outbreaks of BRD in calves aged 10 to 50 days. The cow herd was routinely vaccinated annually with a modified live virus vaccine for IBR, BVD, BRSV and PI3 viruses, which is typical in many cow-calf operations.

At birth, calves were randomized into two groups for comparison.

The bovine coronavirus group (447 calves) received a three-millilitre intranasal dosage of a modified live bovine coronavirus/rotavirus vaccine (Calfguard, Zoetis Canada) within 12 to 24 hours after birth.

The control group (439 calves) did not receive the intranasal coronavirus vaccine at birth.

It should be noted that although this is a common commercially available vaccine, it has not been approved for intranasal use, although it has been used in this manner in other studies.

Both vaccinated and control calves received a modified live intranasal vaccination containing IBR, PI3 and BRSV shortly after birth, which was the routine vaccination strategy on this ranch.

At approximately 49 days of age, calves in both groups were given their routine pre-turnout vaccinations, which included a modified live viral vaccine for IBR, BVD, BRSV and PI3 virus along with mannheimia hemolytica bacterin and a clostridial vaccine that contained hemophilus somnus.

The bovine coronavirus vaccine calf group also received an intramuscular booster dose of the same vaccine they were given at birth intranasally.

The researchers monitored how many calves received treatments for respiratory disease.

Calves were treated if they had two of the following clinical signs: lethargy, drooping ears, cough, nasal discharge, respiratory distress or a rectal temperature greater than 39.9 C.

They also recorded which calves died, although post-mortems were not performed, and the ranch staff recorded calf weights at the time of weaning.

The verdict

Within the bovine coronavirus vaccine group, they had to treat 16 per cent of the calves for BRD, and within the control group they had to treat 22 per cent of the calves for BRD. This difference was statistically significant, which means that is probably not just due to chance.

The researchers also found a reduction in mortality in the coronavirus vaccine group but only within the calves born in the second cycle.

Finally, the calves in the coronavirus vaccine group were two kilograms heavier at weaning than the control group.

This is a great example of a clinical trial that is performed on a commercial herd situation that helps to answer a very specific question about vaccine strategy.

These types of studies in cow-calf herds are few and far between, and Erickson and his team should be congratulated for their hard work in producing this research.

This vaccination strategy with a coronavirus-rotavirus vaccine appears to have some efficacy in certain situations where neonatal respiratory disease is a problem.

It doesn’t eliminate the BRD problem, but it does lessen the number of calves needing treatment and seems to have some impact on death loss and weaning weights.

Coronavirus may have been one of the viruses that was a factor in this herd’s BRD outbreak.

As always, speak to your veterinarian about the best strategy for vaccinating your own herd.

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Biological assays are methods for assessing the presence or biological activity of a substance in living cells and biological matter.

Tim Dumonceaux of AAFC said many pathogens are important for crop and animal production, and those are the ones they prioritize with assays.

Why it matters: Biological assays offer quick identification of pathogens.

We “develop and validate the assays and the model that we followed to make them available to producers is using a licensing approach, not so much a patent approach,” Dumonceaux said during the Ag in Motion farm show in July.

“This is so that companies can pick up the assays and offer them to the producers and package it in a way that will be relevant to them.”

Dumonceaux said systems that use these assays to test samples for specific pathogens can be simple to use with little training and can be conducted in the field or barn.

At Ag in Motion, AAFC displayed a few methods of using the assays to see if the DNA of a pathogen is present in a sample. Visitors to the booth could test samples for signs of sclerotinia in the air.

The samples were put in an assay and visitors could choose among three methods to find out if sclerotinia DNA was present.

A low technology method of DNA extraction involves samples placed in vial with the assay. If the solution changes colour, it indicates sclerotinia is present.

There were also more complicated solutions where a sample is placed in a machine that indicates whether the target pathogen is present. An even more advanced machine sequences all the DNA in a sample.

Dumonceaux said sampling strategies will vary depending on which pathogen is being investigated.

For instance, if a grower wanted to find out if fungi was present in stored grain, it’s possible to develop an assay and sampling technique that can detect the fungi before visual signs appear.

“You could do something like wash the outside of the seed with … a buffer with the light detergent in it to knock off whatever organisms are associated with seeds. We’ve done that in the past to get the bacteria and fungi that are associated with the seeds and you can detect pathogens in that way,” Dumonceaux said.

Plant tissue can also be tested, a strategy he used in his study on blueberry diseases in Quebec.

This study used the same molecular techniques to develop assays for blueberry stunt disease that’s caused by a phytoplasma, which is closely related to the bacterium that causes aster yellows in canola.

Dumonceaux said it’s possible to monitor the geographic distribution and spread of the pathogen in blueberry production fields, as well as the movement of the pathogen within and among plants.

“We use leaf samples from the actual plant itself. So, you clip the leaf off the plant and you can do the DNA extraction there in the field, and then you can do the actual detection assay and get the results back in just a few minutes,” Dumonceaux said. “We think it can work for other diseases as well.”

A separate display at the AAFC booth featured a project by Tara Funk that uses the same molecular techniques to detect bovine respiratory disease in cattle.

Funk is a PhD student at the Western College of Veterinary Medicine at the University of Saskatchewan, and she said BRD costs the beef industry in North America $800,000 to $900,000 every year.

“I am using a new type of diagnostic test called recombinase polymerase amplification (RPA), which uses specialized enzymes at a constant, low temperature to identify a DNA target of interest. Our team is developing new assays to identify bacteria responsible for causing BRD and will apply them to nasal swab samples that we took from beef calves on arrival at a feedlot,” Funk said.

The test provides results approximately 30 minutes after the DNA samples and RPA assay enzymes are combined.

“The machine is very straightforward,” Funk said. “Above all, what it does is provides us with information that we can get to producers and veterinarians on how to make an educated choice on the antibiotic that they might use to treat their cattle.”

A version of this article appeared in the Western Producer.

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That’s the question Dr. Jenna Funk, a beef cattle veterinarian at Texas A&M College of Veterinary Medicine & Biomedical Sciences’ (CVMBS) Veterinary Education, Research, & Outreach (VERO), posed during Grey Bruce Farmers’ Week in January. 

An ancillary therapy is a non-antibiotic product given with an antibiotic to enhance antibiotic efficacy. These therapies can shorten duration of treatment, reduce instances of retreats, relieve inflammation, block histamine activity and boost the immune system. 

Why it matters: Ancillary therapies are often prescribed to help enhance antibiotic effectiveness, but research on how well they work is lacking. 

“The main struggle we have with ancillary therapies is … whether or not we have controlled studies that look at their effectiveness and what they actually do,” said Funk. “Without research, we don’t know what their true effects are.” 

The challenge is weighing the cost of treatment against the financial improvement outcome, whether that’s a reduction in retreatments, chronic pneumonia, dead animals, or to improve the ADG/FE. 

Funk said a 2011 Terrell feedlot consultant survey revealed that 47.83 per cent of veterinarians recommended some type of ancillary therapy, with Vitamin C, Banamine, antihistamines and probiotics being the most popular. On a lower scale, viral vaccinations, B-vitamins and Dexamethasone were also prescribed. 

Only Vitamin C, Banamine, viral vaccination, Dexamethasone, Meloxicam and Ketoprofen have published controlled research, she said. 

Injectable Vitamin C can improve neutrophil function and reduce the case fatality rate, but it requires at least double the label dose to gain effect. 

A 1985 research study showed when vitamin C was given to steers treated with Dexamethasone to suppress the immune system, the immune cells, while not increased, were able to function better. A secondary Australian trial in 2008 found animals treated with Vitamin C had a case fatality rate (CFR) of 11 per cent compared to 23 per cent in those without. 

“This is a statistically significant difference,” she said. “So, we feel pretty confident that Vitamin C is probably helping reduce the case fatality rates.” 

According to the label, Vitamin C is dose-dependent at approximately 2500 mg/animal; however, in 2015, an Oklahoma State research trial of ancillary therapy versus none showed Vitamin C at label doses had no effect. 

So what dose should be used? According to Roth’s 1985 study, “the more you use, the bigger effect you got.” 

Meloxicam treats pain and reduces inflammation in calves with diarrhea or disbudding of horn buds in calves less than three months old. Additionally, it’s administered to treat inflammation and pain associated with acute clinical mastitis, and abdominal surgery such as caesarean section, said Funk. 

“Meloxicam has the potential to reduce lung lesions and create a heavier finished animal,” she said. “Ketoprofen has limited research that it may help reduce lung lesions, but we aren’t sure about that. But we do know it doesn’t improve treatment response when you add it in Draxxin KP.” 

A 2005 study of calves treated with injectable Meloxicam and oxytet versus oxytet alone showed a lung lesion rate of 0.5 per cent for the meloxicam group compared to the controls at 2.28 per cent. They also outperformed in final body weight and carcass weight at 22 and 12 kilograms heavier, respectively. 

If we reduce lung lesions, we improve the animal’s performance and increase the financial gain, she said. 

“That is a legitimate economic benefit with using Meloxicam,” said Funk, adding if live cattle were going for $1.32/lb, that 22 kg of live weight would result in a $63.89 benefit. 

In the U.S., it would cost 15 cents per 100 lbs. to treat with a 15 mg Meloxicam tablet which equates to a 1,600-lb. steer treated for $2.40 compared to an injectable or oral drench which runs two dollars a millilitre. 

Fever in calves is nature’s response to infection by creating an inhospitable environment for bacteria and viruses; by removing fever, you handicap the normal immune response. 

She said that while sick calves do not die due to fever, they do die because of overwhelming respiratory infection. 

Average textbook temperatures for a calf range from 101 to 102.9, said Funk, adding that’s not entirely accurate because environmental temperature, meal timing, and feed content along with exercise can impact it. 

She said if you chased a calf seven times around the pen before getting it into the chute, the elevated temperature may or may not be related to an infection. Alternatively, it is perfectly normal for a black-hided calf standing in the sun, on a sweltering day, with a rumen full of high energy feed to have a rectal temperature of 106, she explained. 

“We do not see organ damage or negative impacts of fever until their internal temperatures reach about 108; anything less I’m okay with,” she said. 

The four studies available of Banamine, a non-steroidal anti-inflammatory often used to control BRD-associated fever, showed no economic improvement to justify the added cost because you get the same result with antibiotics alone, said Funk. 

While effective at knocking down a fever quickly, Banamine is caustic and creates irritation at the injection site when applied subcutaneously or intramuscularly. In addition, Funk said it produces more pain than relieving it unless injected into the vein. It also increased the meat withhold from four days to 30 when injected into the muscle. 

She said that the steroids Dexamethasone and Pred-F are immunosuppressive and can worsen treatment outcomes and suppress immune systems when they are needed to function their best. 

Funk said there’s only one published viral vaccine trial and it showed no improved outcomes. 

“We have six ancillary therapy treatments that have some research on them, some of it’s not great, but everything else has got nothing,” she said. 

“Without peer-reviewed or controlled research trials, it’s very hard to determine whether or not those other ancillary therapies are worth their while.”

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