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If you haven't listened to episode 102, go back and listen, so you have the background for this episode. I promised a follow-up on a previous case study about calf mortality, and here it is. Listen to find out what is happening now!
Hosted by members of the University of Minnesota Extension Beef and Dairy Teams, The Moos Room discusses relevant topics to help beef and dairy producers be more successful. The information is evidence-based and presented as an informal conversation between the hosts and guests.
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Dr. Joe Armstrong: Welcome to The Moos Room, everybody. Dr. Joe Armstrong here with the University of Minnesota Extension. We are doing an update today. We have an update on a previous episode. If you haven't listened to Episode 102, go back and listen to that one. That's going to be key to this episode. I promised an update on what was going on with the case study we went over in that episode and here it is.
We talked in that episode about fixing some of the common things that we see wrong, including bunk space and water space, and then a little bit of the flow that it's connected to how cattle move and how calves move around the time of calving. Well, since then, we have had another calving season and things initially appeared to be going much better. Calves were being born just fine, we had good health, not as many twins, not as many dystocias, a lot of things going right.
I was really excited. We had fixed a lot of the things that we thought were wrong. We had heard hoofbeats and looked for horses rather than zebras. I thought we had a really good handle on things, but unfortunately, I got a call from the same producer and said, "Hey, a lot of stuff is going wrong and I can't really put my finger on what's going on. We're having calves die left and right and it doesn't seem to have any connection to age, or a specific disease, or anything like that. I need help. I don't know what to do next." A really frustrated producer.
A lot of things going on in his farm, everything really looking like they're doing everything right and just not being able to catch up, still having mortalities, and I can't think of a more frustrating situation for a beef producer. You know me, I wanted more information. That's the first step in any of these things when you're trying to solve the problem. We need to know more information.
What age calves are dying? What are they dying from? That's the basis for what we need next. Are they out of heifers, are they out of cows? What is the body condition on our cows looking like? How did the bunk space go? Did we get more bunk space last year? Did we fix the water space? All of the calf flow problems that we talked about in episode 102, is that resolved? The answer was yes. All those things were resolved. Body condition was looking great. Everything was looking good and just things were going wrong.
Our age of calves dying was much different than previously. We have calves dying later after we know that they are probably okay when it comes to colostrum and having that immunity from colostrum. They're dying of things that don't seem to be connected in any way. We have scours, we have respiratory issues, we've got fluke things, but we can't find anything wrong on necropsy. There's just a lot of weird stuff going on and it seems to be at all different ages, all different statuses when it comes to health, some of the best calves dying, some of the worst calves dying, no rhyme or reason to it at all.
When I hear that, we have to look at, okay, well, what could it be? If we have a lot of scours going on in our older calves greater than 21 days old, or even older when we're talking a couple of months, three months, four months. Calves that we think are out of the woods and then we're having them die. Now if that's scours related, then we start looking at coccidia, and that comes down to mud, which we know we had a problem with this year because of the spring.
We need to run that down first and then we need to look at our respiratory deaths. What are we seeing on those respiratory deaths? How quickly are they going downhill? What do those lungs look like on necropsy? We did. We got all that ran down. We had some calves opened up. I wanted pictures of lungs, which we got. Lungs looked really clean even though they were breathing hard. Now, that comes back to we see a lot of calves breathe hard when they're dealing with scours because of the acid-base balance that's happening in their body.
They become acidotic. One of the ways that our body tries to get rid of extra acid in our bloodstream is by getting rid of more CO2 because CO2 is acidic. When we are trying to get rid of CO2, that means that we're going to breathe faster and we're trying to push more CO2 out of the body. A lot of times calves that are scouring are acidotic and they look like respiratory issues, but they're actually just breathing harder because of complications from scours.
That's where we decided to focus first. We need to find, is there coccidia going on, is there a lot of things going on there? I asked for pictures of lungs, head. The producer themselves actually opened these calves up and sent me pictures and the lungs looked pristine in a lot of these calves. They looked absolutely pristine, but we were still having calves die. We weren't picking up a lot of coccidias, but it was there when we were sending in samples. It's possible coccidia played a role in this and I think it still did, but what really got me when we were looking at this situation is that there doesn't seem to be any rhyme or reason.
The farm is clean, there's not that much mud, the calves are out on pasture and things are still going really wrong. I'm going to come back to one of the things that one of my professors in school and a friend now, Dr. Jeremy Scheffers said, BVD, Bovine Viral Diarrhea virus makes good farmers look bad, and smart people look dumb. That's exactly what's going on here.
There's a lot of things that we can't explain. There's no rhyme or reason, no pattern, and what we're seeing is cows die from a lot of different things that are relatively unexplained and there's no pattern like I said. When I see that and I see that the timeframe does not match with another disease process, we have to be thinking BVD. BVD causes generalized immune suppression. You see calves die from a lot of different things with no real pattern, it affects all different ages, it affects all different time points in your farm.
You can't identify and push it to a specific flow with your calves moving. It just fits when you've eliminated everything else and you have a farm that's looking really, really good doing everything right and they still can't quite make it fit. We have to check for BVD when that's the case. At this time point, that's the plan, we're going to sample for BVD in this herd.
Now, BVD can be a transient infection where it just comes through the entire herd. Works through it just like a normal virus would and you have a pretty defined period. Now, it usually works through herd pretty fast if that's the case, between two and three weeks is usually how it works through a herd if they're all pretty tight quarters. Now, in this case, these problems have been going on for quite a long time and potentially over the course of several years.
When we're looking for BVD in this herd, we are looking for persistently infected calves. BVD is a scary disease when it comes to your pocketbook because you get calves that can hide and be the source of BVD in your herd, and continually shed virus as a persistently infected calf. The scary part about that is that they can make more of themselves. You get more virus factories in the form of calves when you already have one in your herd. Persistently infected animals are created when BVD is present during a certain period of pregnancy. You can have a cow be pregnant with a calf and when they get into a certain period, we're looking at 120 days pregnant is what I have in my mind, that calf is basically taking inventory of everything that's there. Everything that's present at that time, they're going to consider self. They're going to say, "Okay, everything that's here is supposed to be here, and I'm going to say that this is now something that should be here, and I'm going to consider this my cells, that's myself."
If BVD is present at that time period, they then consider the virus, that calf considers the virus part of themselves. When they eventually hit the ground and they come out, they produce this virus just like it's a normal part of their body. Some of these calves look ragged and a little unthrifty because of the extra pressure of producing that virus constantly, but a lot of them don't. A lot of them look 100% normal and you'd never ever know that anything was wrong with them and that they're producing this massive amount of virus that's going to affect all of the herd mates around it and continually create immunosuppression in your entire herd just from this one animal.
Now, the real scary part is when you get a persistently infected animal there and then they stick around for the next breeding season. Now there's BVD present at all times, and they are going to be there during that period of pregnancy for the next generation. Now they have the opportunity to create more persistently infected calves. Then the next calf crop comes and you get several more persistently infected calves hit the ground.
Now you've taken what was already a huge amplification and the source of this virus and you've made it even bigger. You can see how this might snowball and get out of control and create havoc that you just can't get a handle on and be super frustrated and make you honestly want to hang it up. Get rid of the cows, I just can't deal with it because there's no way to figure out what's going on unless you start testing for BVD and you have that on your mind. Super frustrating disease process.
In this case, I'm fairly certain that this is what's going on. This farm is just too good. The people are too smart to have all these things going wrong with no rhyme or reason to it. I'm fairly certain we're going to come back positive with some PIs in this group.
Now, in terms of sampling, what do we need? Here's the plan. This is how we're going to approach sampling this herd. This is a pretty standard approach for how I like to sample herds, to track down BVD PIs and try to do it in a way that's not going to break the bank when we're talking about the cost of sampling and sending those samples in for testing.
What we usually do is start with calves. We need an ear notch from every calf that's on the farm. The goal is to find PIs, and if the dam is a PI, then it will produce a PI calf. If I test all the calves, the negatives mean that the dam is also not a PI. The dam can't be a PI because the calf is negative for BVD. Basically, I'm getting two-for-one testing by testing the calves. If they're negative, that means their dam is negative as well. If they're positive, it's possible, but the dam is also a PI, so we need to go back and test the dam of the positive calf. Now, the way that we try to make this even less expensive is to pool samples.
The way we test for BVD is with PCR. PCR is an incredibly sensitive test. We can actually put multiple samples together and then see if that pool of samples is positive. If the whole pool's negative, then it's truly negative, and I don't have to worry about any of those animals. If the pool's positive, then we go back and we test each individual animal in that pool of animals to see which one caused the positive in that pool. Just a way that we can usually take the cost of testing down quite a bit. Usually, when we're looking at pools, we're looking at pools of 50 being the max. That is really dependent on taking good samples, though. We need to pool samples of 50, test those pools. If they're positive, we'll go back and individually test each animal in that pool.
Like I said, the ability to do this is dependent on taking good samples, so we need a big piece of ear, unfortunately, a half-inch ear notcher works really well. Then we need to put that in a red top tube that has no other gel in it. Red top tube, standard red top, usually a 7 or a 10 mil red, half-inch ear sample from every calf. We need to be extra careful to label everything accurately and clearly because it's very, very important that we can identify these calves later when we come back with positive results potentially.
The goal when we sample is to make sure that we're covering the entire herd. We're testing every calf in the herd, but that means we also need to test any animals that don't have a calf. We need to test any cows that are around that don't have a calf yet, all of our replacement heifers, and if we have any bulls on-premises, those need to be tested as well.
The other thing we can't forget about is that some people have a fall herd. If you have a fall herd, we have to do the same process in the fall herd because, like I described before, one missed PI can set this whole thing rolling again and can cause a disaster, so we need to have a test on every animal and the calves that have a dam on the premises, and we know that they're correctly identified, that counts. We need to have some kind of information on every single animal because if we miss one and that animal turns out to be the PI, we're in trouble, and we haven't fixed the situation at all. We've got to find all the PIs, and they've got to be gone to make this all work.
Now, one of the questions that I get all the time when we're looking for BVD is, where could it have come from? How did it get here? Now, I think it's a good exercise to think about that so that we can learn more about biosecurity, but it can be super frustrating trying to figure out where it came from. I don't think it's very beneficial to try to figure out how to point the finger at a certain part of your operation or at a certain person or anything like that. I don't think that's very beneficial because there's so many different ways that BVD can show up on your farm. Buying animals is the number one way to do it.
On dairies, we see it a lot where people are buying bred heifers or bred cows, and the cow is negative, but the fetus is a PI. You're looking at a negative cow carrying a PI animal, so you're buying a PI animal that you can't test yet because it isn't on the ground yet. Bought animals are the number one way that BVD comes into your farm. Now, you can also have nose-and-nose contact on pasture with another herd. You can go to shows and bring that animal back. Any way that we would have not a closed herd means that BVD has a way to get in.
Now, something that we don't know a ton about yet is endemic BVD. Some animals carry BVD in a non-cytopathic form for quite a while before it turns to the cytopathic form of BVD and starts causing problems. Sometimes, you can have animals that have had BVD, and they potentially are a PI, and they've been carrying this for a long time, but it's not the cytopathic version of BVD. You don't have problems in your herd in a big way until something happens, and that changes to the cytopathic form of BVD, and then everything hits the fan, and everything goes wrong. We're still learning about that piece.
We don't know all about endemic BVD yet. They're still investigating it, but you can see how that adds a layer into where did it come from? How did I get it? and where I think it doesn't make a lot of sense to try to figure out where to point the finger. I think it's great to talk about because you need to understand biosecurity and all the risks that you're taking in not having a closed herd, but again, I don't think it's beneficial to try to figure out where to point the finger.
Now, the big question, the biggest question. I vaccinate, why am I not protected? Well, this herd is very good with vaccination, and they're still most likely having a problem with BVD. Vaccines, like we've talked about before, are not a silver bullet, they're not the absolute solution. They can be overwhelmed. Vaccines are really, really good at preventing the development of BVD PIs in utero, but again, they're not 100%, and they can be overwhelmed. If you have a PI standing there next to a vaccinated animal and they are continually exposed to a massive amount of virus, the vaccine is going to help, it's going to help prevent, it's going to mitigate the situation so that it's more manageable, but it doesn't necessarily mean that you're 100% protected in all situations.
Now, we'll find out if this herd is positive. If there are PIs, we'll be able to comment on this further because this herd is so well vaccinated, and then they still have PIs in the group. That tells you that probably the vaccine's going to have mitigated it, made the problem smaller, and made this whole situation less bad, but it wasn't 100% effective in preventing everything, which is exactly what we're counting on vaccines to do. We want them to mitigate the situation, make the risk smaller, become insurance, but we can't count on them to be 100% preventative for everything all the time.
All right. I've given you a lot to think about today, trying to provide an update on this case. We will continue to update this case as we get more information as the testing comes in. I'll let you know exactly what's going on, my thought process on how we're going to solve this, where we're going to go next, how long this whole thing's going to take to get it wrapped up. Like I said, BVD is a disease that makes good farmers look bad and smart people look dumb.
Any time where you really feel like you've got a handle on everything and everything's going really, really well, and then you have this weird deal that you can't connect to the weather or disease process or stress or anything else, and you're having all these weird things go on, you need to be asking yourself, could BVD be causing this?
It's a very frustrating situation, and in some ways, I want these tests to come back positive because it will give us an answer for all the things that are going on in this farm that I can't explain yet.
Obviously, in some ways, I want it to be negative, and then we have to go searching again and try to figure out, okay, what else could be going on if it's not BVD. If it is BVD, it's going to be a long process to get rid of, somewhat expensive process to get rid of, but much less expensive than leaving those PIs in the herd. We'll talk more about this whole situation, what to do with PIs, what to do next if we are positive as we move forward. Stay tuned as we update this, and I'll keep you guys in the loop on what's going on.
With that, if you have comments, questions, scathing rebuttals to this episode, please email themoosroom@umn.edu. That's T-H-E-M-O-O-S-R-O-O-M@umn.edu. If you would like to leave a voicemail and have your question included on the podcast, please call 612-624-3610. Check out our website extension .umn.edu. Check us out on Twitter at @UMNmoosroom, and @UMNFarmSafety. If you'd like to see what's going on up at Moos, look on Instagram, find Bradley's account, @umnwcrocdairy. That's all I got for today. Thank you for listening. We'll catch you guys next week.
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