Can we prevent feedlot viral respiratory disease?

The feedlot industry still struggles with preventing and managing cases of bovine respiratory disease and the strategies for preventing or lessening viral diseases.

Many agree that if calves can be pre-conditioned or backgrounded and prepared for the feedlot that they may be more immunologically competent on arrival. This can include being vaccinated, weaned, castrated, bunk broke and other strategies, but there are costs associated with that.

Around eastern Nebraska/western Iowa, many backgrounding operations hold 800 to 2,000 head, says Kelly Lechtenberg, DVM, PhD, Midwest Veterinary Services, Oakland, Neb. "In these yards, folks could take some animals that are younger and potentially at higher risk," he says. "They have a smaller biosecurity envelope; they have lower pathogen exposure potential than larger operations. The cattle have an opportunity to be prepared immunologically for a more challenging environment in the feedlot. The tradeoff comes in terms of cost. The labor and economics associated with more intensive management results in higher costs than if they just bring them into the feedyard."

In Canada, Feedlot Health Management Services, Inc. (FHMS), Okotoks, Alberta, has clients who feed a lot of these high-risk populations. "We've got this big bulge of cattle come through the sale barn system at one time," says FHMS" Calving Booker, DVM. "From a buying perspective it's usually the cheapest time that you can procure your feeder cattle all year, so now you have to figure out where am I going to put them all because I don't have room in the feedlot so they've got to put them out to various locations."

Every fall in Lechtenberg's part of the country, where calves are received seasonally, he makes the assumption that most of the yearlings coming at him from grass systems have had some type of viral vaccination programs. "I expect that grass cattle have usually seen at least one dose of modified live vaccine," he says. Weaned calves that are purchased in the fall are often marketed with vaccination history available. This is nearly always the case for direct sales from the ranch and increasingly true of large group auction calves. "When we purchase calves that originate from very small operations and are purchased in small groups, we have less or no history and don't put much confidence in the history when available. The lack of knowledge of what's been done is certainly a hurdle for us."

The question Lechtenberg would really like to know the answer to is how well these cattle are protected against a viral epidemic. "Vaccination history is valuable information, but still fails to provide the desired information because we don't know if all of the other important factors were optimal or even acceptable," he explains. "Was the timing appropriate relative to maternal status? Were stress levels in the calves acceptably low? Was nutritional status of the calves adequate for an appropriate immune response? Had the vaccine been handled and administered properly?"

The overall effectiveness of the pre-arrival vaccination program is always a bit in question, but Lechtenberg says he certainly would rather have those calves vaccinated than not vaccinated. "It is really important that an organized program transfers information, including timing and nutritional status of the calves that were vaccinated. With improvements in information systems available, I am confident that the important information will be increasingly available on more cattle. I believe that this will happen because it is important and adds value. Our current system is not perfect. Our industry has made significant progress in this area over the past several years."

Earlier the better for vaccination

The paradigm to pre-arrival vaccination of Shawn Blood, DVM, Hitch Consulting Service, Guymon, Okla., is that the feedyard is probably the worst spot for vaccination, the stocker level is better, and then cow-calf level is even better. "The earlier the better," Blood says. "The earlier before you get a lot of exposure is better in my paradigm. We do see some cases in which we think the cow-calf producer or the stocker producer is doing very well, but the year-to-year variations are often times a huge spread so we scratch our head and wonder what's going on and why it's different from year-to-year. We think we can figure some things out sometimes, but in general it's tough to sort all those confounders out. I believe the earlier we can get those vaccines into those cattle, the better the long-term immunity is in those herds."

Records on calves can be few and far between which causes feedyards to have to guess or just assume calves are naïve. "We get records accompanying some, but that would be a very small proportion of the cattle that come in," Booker says. "On the stocker side, you probably get better records and the history of what has happened vaccination-wise than on the cow-calf side. For the few retained ownership programs, for sure you get the records."

Booker says if you look at the sero-epidemiology studies, having higher antibody titers to respiratory viruses when cattle arrive at the feedlot lowers the risk for subsequent disease. "How we get to pre-arrival vaccination is based on these findings plus our first principles approach," he says. "There are very little data, if any, that actually fills that gap and shows that if we pre-vaccinate groups of calves versus the same cohorts that are handled the same but not pre-vaccinated the impact is X. That's part of why we're always trying to get our hands around it and put a number to it."

Booker says usually the owners that go through the process of pre-conditioning and vaccination also do a lot of other management things to prepare the calves or feeders for going to the feedlot. "I don't think there's any doubt that the net effect is positive, but I don't think we know how big or small it is," he says.

Lechtenberg agrees that the data is scarce and that there's an inherent bias in the research. "The data that's out there will tend to underestimate the value of vaccinations, for all the reasons Calvin just mentioned. As we look to well-controlled research to provide results that help lead us to making informed decisions in the feedlot, we must realize the similarities and differences between the two populations. High-quality research will need to be conducted to meet all the criteria that we respect and has data integrity associated with it."

Dan Givens, DVM, PhD, Auburn University agrees that the impact of an effective vaccination protocol is significant. "I would also add that, working with different cow-calf operations, the impact of an ineffective vaccination protocol is not significant. I think sometimes management aspects confound the decision-making process of individuals. For instance, we see some cow-calf operations that only administer one dose of vaccine before three months of age to a group of beef calves. When you look at the available data, in a dairy calf with declining colostral antibodies maybe there's a little bit of stimulation of cell-mediated immunity in those calves, but by the time beef calves go through the stress of shipping and weaning at six to seven months of age, and are sent to the Midwest from the Southeast, I don't believe that's an effective vaccination protocol."

So as we address the question of "what is the impact," Givens agrees that the impact of effective vaccination is significant. "I also feel like there's a group out there who needs to understand that one dose of killed vaccine, which is totally off label, is not an effective vaccination protocol. The resulting protection from this off-label vaccination is not significant, so please don't use that in your data set of assessing whether or not an appropriate vaccination protocol is effective."

Lechtenberg says large herds are very motivated to add value, since cattle production is the primary economic driver in those operations, and tend to use more inputs in calves. "The concept of retaining ownership is the ultimate tool driving proactive health and performance programs. We see the highest incidence of non-vaccinated calves originate from very small production systems. In general, owners of small groups of cows are inherently less motivated to commit the time and energy to improving the immunologic status of their calves. When the calves look good and are healthy, many owners may value a weekend at the lake with their family more than spending all day Saturday gathering, sorting and conducting a pre-weaning vaccination program on 20 calves that might bring an additional $5 to $10 per head for their effort. Our health programs need to be targeted to the lowest common immunologic denominator and that is getting all of them vaccinated."

Developing risk categories

Many feedlot health and treatment protocols involve developing risk categories for incoming cattle. Blood says his feedyards typically have two or three. "The simplest one would be low risk and high risk and our management decision is: are we going to use metaphylaxis on them? And then we can break it down a little bit more deciding on which drug to use for metaphylaxis." It's important, he says, that there be a management decision assigned to each category and applied to the animal being scored. "If there's not, then there's no reason to have another risk category. Right now most of the tools we use for classifying cattle are pretty subjective categories."

Blood says he cattle foreman typically has acquired all of the history and information on incoming cattle and makes the decisions on arrival processing protocols. Size (a proxy for age), how far they've been hauled and how much commingling they've had would be the factors that would play into processing protocols. "For a lot of repeat customers who feed a lot of cattle, you automatically know just the class of cattle he's going to feed and the type he buys," he says. "Just as soon as you hear his name you know what classification those cattle are going to be as far as high versus low risk."

Booker thinks risk assessment takes place at the group level and results in a population risk number of the probability a group of animals are going to be low-risk, medium-risk or high-risk. "You can have two categories, you can have five categories; we've probably got five," he says.

Within Booker's systems, demographics of the arriving cattle are noted such as: what's the source, who is the owner (this has implications relative to how they source cattle), how big are the cattle, what time of year is it, what gender are the cattle, how big is the group size, etc. "In our case, the cattle manager and even the processing supervisor just execute the plan," he explains. "To execute five different processes with five different risk categories in a day is no big deal. It's a work order that comes down and needs to be filled."

The population-based risk factors are probably pretty accurate, Booker says. But at the individual animal level they are not very accurate. "For individuals within those populations, there are probably some animals that get a tremendous benefit from metaphylaxis and immunization programs, and there are others that probably get very little benefit. Our next challenge is to get to the individual level. Can we really identify those that are at an extremely higher risk than the group average and those that are at an extremely lower risk? If so, there are probably some major things we can do to manage cattle differently."

Vaccinating on arrival

It's a common practice for feedlots to vaccinate incoming cattle on arrival or within a day or two. Blood typically likes to have them vaccinated the day after arrival. "If they came in at 3pm today we'd probably work them tomorrow. Depending on what all's going on it might be the next day but it's usually the day after arrival."

Lechtenberg says if cattle arrive on a Saturday, they would probably sit until Monday before being vaccinated. "If we pull cattle out of local farms with a short drive and it's early in the day, they might get vaccinated off the truck, but typically the next day," he says.

In Canada, Booker says cattle are vaccinated within 24 hours of arrival. Similar to Lechtenberg, if cattle arrive early, they might get processed the same day. Saturday arrivals will usually wait until Monday, but some feedlots, Booker says, especially if they are dealing with high-risk populations, will go ahead work high-risk groups on Sundays.

From an immunology and stress standpoint, John Ellis, DVM, PhD, Dipl. ACVP, Dipl. ACVM, Western College of Veterinary Medicine, University of Saskatchewan, adds that the worst time to vaccinate is when it's most often done. "With all the talk we've done over the years, it's still done. For the practicing veterinarian in the feedlot, it's about the only thing that can be done. It reminds me of Einstein's quote about insanity, ‘Doing the same thing over and over again and expecting a different result." That's where we are with vaccinations on arrival."

Booker says there is a lot of anecdotal work done with different groups of cattle and arrival vaccination, but it's highly confounded with different risk categories, different times of year and different vaccines. "I'm not really sure we can sort that out," he says. "If you look at the studies that have Pasteurella/Mannheimia, BVDV, and BRSV components in vaccines, those studies have all been done on arrival, those cattle have all been processed at feedlot arrival more or less as per the standard approaches each of us just described previously described, and they've shown cost-effective responses to doing so. Could you get a better response if you waited and did it 24 hours later or 48 hours later? It's possible."

Another reason to not wait too long is because at processing, especially for the higher risk populations, we're doing other interventions to control disease such as metaphylaxis. "The longer we wait, the less effective those products probably become because disease is happening before your eyes," Booker says. "And we're always behind the eight ball in those auction market situations."

So realizing that stimulating the innate immune system with a modified-live vaccine can give you some significant protection against IBRV and BVDV at 3–5 days after vaccination, and knowing those animals are out of a feedlot's control in those 3–5 days prior to arrival, Givens asks if there is a potential to move that window at all just to get those animals vaccinated, before arrival.

"If you could set up the physical logistics of having the procurement system being able to do that reliably, you could," Booker says.

Economics and vaccination

If cattle already have antibodies at feedlot arrival, they are at a lower risk of subsequent morbidity, according to seroepidemiology studies, Booker says, even though it really hasn't been tested much for mortality. "If cow-calf producers can do things to deliver calves that arrive at feedlots with higher antibody levels, that's going to reduce the overall challenge level for feedlots to deal with, even though feedlots do other things (e.g., long truck rides, extensive commingling, post-arrival management, etc.) that counteract some of the benefits of higher arrival titers. The challenge is that there's a cost associated with accomplishing this at the cow-calf level and there's a benefit that accrues at the feedlot. I'm not sure that those two are in balance because the benefit that accrues at the feedlot may not be that large or maybe we just don't know how large it is. In most cases, it's probably estimated to be a small benefit for the feedlot; I'm not sure it covers the cow-calf's producer's cost and ‘return on his/her investment"."

The cow-calf producer has put all the inputs into the calf and needs to get paid for that, Booker says. The most direct way is to pay the cow-calf producer a higher price for the feeder animal. "That's where that disparity exists because feedlots can usually buy the ‘same" cattle at a lower cost in the marketplace, manage the higher risk when they arrive at the feedlot, and accomplish this at a lower overall cost/break-even than paying a premium for pre-vaccinated calves. That's the challenge."

Geography and farm size can also play a role in economics and vaccination on the cow-calf level. Givens says beef operations in the Southeast don't have the density of animals on the farm. "We have lots of small farms, we have lots of folks who are making the decisions such as ‘do we boat this weekend or do we work cattle?" Some of those individuals are even looking at the dollars and cents of it pretty carefully and they're looking at if they do go in and vaccinate on a repeated basis, are they getting the increased value? In all honesty, the only way they get the increased value of doing the vaccination is if they add additional time, effort and energy, which goes with dollars, to market those calves well."

Givens says vaccination of calves without marketing will probably not pay off. "So if you vaccinate you're going to have to market, and if you vaccinate and market then it may pay off. But we didn't say it would always pay off so you get into a ‘do you want to invest your money in this or not?""

That being said, Givens still sees increase in vaccination on southeastern farms, but that's driven by farm size versus an actual uptick in the practice overall. "A key reason we have seen an increase in vaccination in southeastern cattle is because we've seen herds sold off," he explains. "The herds that tend to sell off are the smaller herds. The herds that tend to vaccinate and market are the larger herds. I think we have seen an increase in vaccination because we've taken out some of the smaller players. Those who are vaccinating are focusing their vaccination on where it will pay the greatest dividends to them on a cow-calf sector, which is vaccination of heifers and cows to protect their calves and protect reproduction."

Givens believes the industry over estimates the rate of vaccination in the cow-calf sector. He cites a presentation at the American Association of Bovine Practitioners meeting that showed a survey of 100 veterinarians who said that 77% of their cattle herds were vaccinating for respiratory disease pathogens. "When you look at the National Animal Health Monitoring System (NAHMS) data and look at vaccination for BVDV which I think is a pretty good approximation for what's going to be the actual vaccination for respiratory disease, the number is about 33%," he says. "So we have an estimation of 77% of cattle herds that are under consultation with a veterinarian being vaccinated, but the NAHMS survey shows that only 33% are being vaccinated."

Another frustration Givens has with vaccination on the cow-calf side is effective vaccination versus ineffective vaccination protocols. "If you really query the NAHMS data, we, the cow-calf sector, are still giving a lot of single doses of killed vaccine, which means the money that is being spent, the labor that is being spent, is not being spent as efficiently as it should be. Can we improve the health of cattle coming to the feedlot? We certainly can. Should we? It's a dollars and cents game and at the end of the day, it's a business."

Despite the frustration, Givens does think the industry is doing better. "We are making incremental improvements. We still have some operations that are doing it the way they've always done it and partly because they can't justify the additional investment in marketing calves. They don't have an effective vaccination protocol because it does not provide a financial return without an additional investment in marketing calves."

Lechtenberg also believes many producers have been making economic decisions for many years that they are probably very comfortable with. "For example, put $15 a head profit on a 25-head calf crop and throw that into someone's economic model assuming those folks are just as busy with family and work life and everything else and then ask yourself how many weekends are you going to give up with your family for less than $500 when mom and I both have jobs and we're doing fine? Part of our challenge is to recognize pieces of the industry as they are, despite our best efforts and what we think is logical, that maybe isn't going to change for societal economic reasons. It's the same reason people who are drawing unemployment don't go back to work for a paycheck that's smaller than their unemployment check until it's going to run out. It's just a good economic decision." 

This information is from a Bovine Veterinarian roundtable sponsored by Pfizer Animal Health and moderated by Jessica Laurin, DVM, Marion, Kan.

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