BEEF CATTLE PRODUCTION SERIES - PART 3 by TSCRA - The Cattleman Magazine

BEEF CATTLE PRODUCTION SERIES â&#x20AC;&#x201C; PART 3

Weaned Calf and Stocker Cattle Management: A Good Vaccination Program Will Protect Valuable Calves From Disease

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To find the PrimeVAC preconditioning program that’s right for your operation, talk to your veterinarian and visit cattleprimevac.com. Always consult your veterinarian concerning: best health management decisions specific to your operation, selection of qualified USDA/FDA approved products, optimum use of combination products, and the efficacy of vaccination in the face of maternal antibodies. Always read, understand, and follow product label and use as directed. Data on file. merck-animal-health-usa.com • 800-521-5767 Copyright © 2016 Intervet Inc., doing business as Merck Animal Health, a subsidiary of Merck & Co., Inc. All rights reserved. 54670 1/16 BV-PV-51322

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BEEF CATTLE PRODUCTION SERIES â&#x20AC;&#x201C; PART 3

Weaned Calf and Stocker Cattle Management: A Good Vaccination Program Will Protect Valuable Calves From Disease Table of Contents 4 Calf Vaccinations Support Productivity 6 Prepare Stocker Cattle for Success 9 Fall and Early Winter Stocker Cattle Management 11 Histophilus somnus: Prevalent, Problematic and Hard-to-Diagnose Bacteria 12 BRSV: 6 Hours from First Sign to Death 14 BVD Causes Multiple Losses to the Cow Herd

The Cattleman, the monthly journal of Texas and Southwestern Cattle Raisers Association, is pleased to partner with Merck Animal Health on a series of seasonal beef cattle health management manuals. Thanks to the generous support of the Merck Animal Health technical services veterinarians, Dr. David Bechtol and several of his colleagues, we are able to provide a blend of easy-to-read articles that educate and inform ranchers about various aspects of beef cattle health management. thecattlemanmagazine.com

Merck Animal Health BEEF CATTLE PRODUCTION SERIES â&#x20AC;&#x201C; PART 3 Weaned Calf and Stocker Cattle Management 3

Calf Vaccinations Support Productivity By David Bechtol, D.V.M., Palo Duro Consultation, Research & Feedlot, Canyon, Texas, and Dr. Jim Furman, The Animal Center, Alliance, Neb.

The protection of a calf crop really starts with a good health program for the cow herd. The cow is responsible for protecting her calf, first in the uterus and then for the first 2 to 3 months of life. Antibodies in the mother’s colostrum are absorbed into the calf’s system in the first 48 hours of life and protect the calf for the next several weeks. A cow herd managed under a good herd health and vaccination program benefits the newborn calves. Vaccines in the cow herd health program might include protection against diseases such as scours from E. coli, rota and corona viruses, clostridium type C and D, pneumonia diseases, infectious bovine rhinotracheitis (IBR), bovine viral diarrhea (BVD) and parainfluenza 3 (PI3). First vaccinations At branding, or 2 to 3 months of age, the calves can be started on their own health and vaccination program. The first vaccines introduce the calf’s immune system to the diseases they’ll most likely encounter over the next year or so of life.

The more an animal is exposed to disease, either through vaccination or through Mother Nature, the better the immune system develops to protect that calf. Consider exposing your calves to controlled disease with a vaccination program before Mother Nature gets the chance to expose the calf to pathogenic diseases that can often cause sickness and death. A thorough vaccination program includes protection against diseases such as: • Clostridia • Histophilus somni • Mannheimia haemolytica • Pasteurella multocida • IBR • BVD • PI3 • Bovine respiratory syncytial virus (BRSV) Vaccines for all of these diseases may be safely given to calves nursing cows that are still open. Certain vaccines may transfer from the calf to the cow for about 10 days after vaccination. If the cow has been recently bred, this exposure

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may cause the cow to abort the fetus. Protect early pregnancies by making sure the vaccines used on calves won’t cause abortions. Next stages — pre-weaning, weaning and preconditioning If you decide not to vaccinate 2- to 3-month-old calves, consider the value of vaccinating the calves about 2 to 4 weeks prior to weaning at 4 to 6 months of age. This is the preconditioning vaccination that most cattle buyers look for when they want to buy weaned calves to go into a stocker cattle operation or to the feedyard. Preconditioning is a term used in ranching to describe the management of calves during a certain period of time (35 days, 45 days or some other length of time) at the ranch of origin. With a good herd vaccination program, when the cow herd is vaccinated annually with a viral vaccine prior to breeding, a modified live virus (MLV) vaccine booster may be given prior to weaning even though cows are pregnant. The clostridia vaccine is also given pre-weaning, eliminating the need for an additional booster at weaning when calves receive a priming dose at 2 to 3 months of age. If clostridial vaccines are not given in this time-frame, follow the manufacturer’s guidelines on the vaccine label for proper booster administration. Two doses of clostridial vaccines by weaning generally means the cattle will not need another booster dose until yearling age. Other vaccines that can be used pre-weaning or at weaning as either a primary or a booster vaccination are H. somni, Mannheimia and Pasteurella.

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If you give calves their first round of vaccinations at 2 to 3 months of age, weaning is the next time we like to see calves vaccinated in order to boost their immune system. This generally happens the day the calves are separated from their dams and kept at the ranch or at the time they are shipped. If you are backgrounding calves at the ranch, we suggest administering vaccinations for all of the diseases mentioned in this article. This will equip them with the immunities to fight off whatever they may be exposed to at the auction market, stocker operation or feedyard, or until they are given a booster vaccination. Preconditioning can be part of the weaning process, or can start right after weaning to get the calves prepared to be shipped off the ranch. Calves being preconditioned receive a round of vaccinations to initiate their immunity to the bovine respiratory disease complex (BRDC). BRDC causes expensive economic losses due to the negative effects of disease (morbidity) on weight gain or calf productivity; the cost to treat diseases; and death loss from disease (mortality). Consult your local veterinarian about any additional diseases in your area for which your calves should be vaccinated. You cannot always be sure where your calves will end up, so a complete vaccination program will prepare your calves for transition to anywhere. You and your local veterinarian can feel good about preparing your calf crop for any situation they might encounter after they leave your operation. This will keep buyers coming back to look for the healthy calves produced at your ranch. ❚

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Prepare Stocker Cattle for Success The right nutrients and timely vaccinations can help stocker cattle transition well from the ranch to forage to the feedyard. By Gary DiGiuseppe

Once calves have been weaned and are headed to grass, they need to be protected against the pathogens that lay in wait for them. Mark Spire, DVM, has some tips to keep those animals on the road to good health. Spire, retired from a career as a technical services manager for Merck Animal Health, says that in some ways post-weaning calves are in good position to accept a new round of immunizations. They’ve started to develop an adult immune system, so they can respond well to vaccinations. Any residual antibodies from the mother’s colostrum, which protected them they were younger, won’t interfere with this round of vaccinations. In Spire’s experience, he has noticed that calves are generally weaned from August to October and January to February. The forages the calves are headed to at these times of the year are usually low in mineral content. “We may not see the full bang for the buck we’d expect from our vaccinations because the trace minerals — particularly zinc, copper and selenium — may not be there in adequate amounts to maximize the immune response.” This means a good supplemental mineral program is crucial for a forage feeding operation. What is the best way to deliver minerals to calves? Some operations receiving newly-weaned cattle add minerals

directly to the feed. Others provide minerals in a salt-mineral mix. Still others use tub feeders with a molasses-based mix. Spire thinks the molasses tub may be the best route, saying, “The cattle really seem to like and adapt to them rapidly. Even from the first day, they’ll get to those tubs and use them.” Other methods, by comparison, may not provide enough mineral intake. Spire notes that for the first 10 days after arrival, the calves’ feed consumption is usually depressed, so they may not be taking in adequate quantities of the minerals needed to boost their immune systems. He recommends against using injectable mineral products upon arrival of the calves without knowing their specific needs. The injectable mineral may cause injection site lesions and may dampen the calves’ response to vaccines due to inflammation. Critical 2 weeks An upon-arrival trace mineral program is necessary because the stocker operator may not know the management policies at the calves’ previous location. Or the calves may have come from a number of different locations, and that alone can increase the risk of disease. Spire says, “Cattle that are put together by a marketing service, or mixed at an order buyer’s facility and then shipped, have a lot higher risk of disease — not from the way they were

6 Merck Animal Health BEEF CATTLE PRODUCTION SERIES – PART 3 Weaned Calf and Stocker Cattle Management

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Always read and follow label directions.

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2 Giralda Farms – Madison, NJ 07940 – merck-animal-health-usa.com – 800.521.5767 Copyright ©2015 Intervet, Inc. d/b/a Merck Animal health, a subsidiary of Merck & Co., Inc. All rights reserved 10/15 BV-SG-54399 Stromberg, B.E., et al., Cooperia punctata: Effect on cattle productivity? Vet. Parasitol. (2011), doi: 10.1016/j.vetpar.2011.07.030

handled at those facilities, but because when we start mixing populations of cattle, we have a good opportunity to start sharing viruses and bacteria.” On the other hand, while the risk of respiratory infection is lower if calves come from a single source, the “bugs” they’re either carrying or exposed to in their new environment could be activated. Spire says even in operations with an inherently low virus or low bacterial population, “As soon as we put stressors on the animals — the stress of hauling, the stress of mixing cattle, the stress of adapting to the new pens, or new feeds or new water, at their new location — it seems to activate the viruses and the bacteria. Whether they’re commingled and brought in as mixed cattle or come from a single source, those first 2 weeks are absolutely critical in how we manage the calves.” Knowing the vaccination history of the animals is valuable. When they’re processed upon arrival at the forage facility or stocker operation, the personnel can know the calves are now receiving boosters and less risk of illness can be expected. Knowing the history of the calves’ health program allows the experienced operator to look for weaknesses in the prior vaccination program and be prepared to address diseases they’ve seen in the past upon delivery of the calves. “If we don’t know their vaccination history, then we don’t know what level of immunity a calf may have,” Spire says. “So we tend to give a lot of components within a vaccine. That really adds to the complexity of stimulating the immune system and having a calf that’s receptive to activation of the immune system.” Ranchers handling newly-shipped cattle should be aware of infectious bovine rhinotracheitis virus (IBR or “rednose”), multiple strains of the bovine viral diarrhea (BVD) virus, and 2 bacterial diseases, Pasteurella multocida and Mannheimia haemolytica. Depending on the operation, vaccines may also be needed for bovine respiratory syncytial virus (BRSV), parainfluenza-3 (PI-3), and Histophilus somni. And if the males have to be castrated, clostridial diseases, which tend to infect wounds, can produce a systemic and often fatal risk. These organisms include Clostridium septicum, C chauvoei, C perfringens, C novyi and C sordellii. Spire says a typical program for newly arrived calves will incorporate a 5-way viral, a multi-component Pasteurella/Mannheimia vaccine and a multi-component blackleg vaccine. Calves should also be dewormed upon arrival. If the history of the cattle is unknown, Spire says, “They may be coming from multiple parts of the country. The odds are, through the summer, they’ve picked up a fairly significant parasite load.” The benefits to deworming include improved weight gain and performance of the animals and, he says, it will actually stimulate the animal’s immune system.

What’s the weather going to be like? Another issue is the time of year. The majority of the U.S. calf crop is still born in the spring, so they get moved to grass operations in the fall. Forage quality and trace minerals will have declined from where they were earlier in the year, causing the calves to experience nutritional stress. And then, as Spire says, there’s the weather. He says, “You’re suddenly moving cattle from the southeastern part of the U.S. or Texas to Kansas or Nebraska in October or November. At this time of the year, we start getting warm days and cold nights, with rain and occasionally snow. These cattle haven’t adapted to that type of environment and it actually puts a major stressor on them.” This kind of weather means the calves need even higher caloric and protein contents in their diets just to maintain their normal bodily functions, and Spire says the receiving operation often hasn’t adjusted feed delivery to anticipate that extra need. Some calves will be off their feed for the first 2 weeks after arrival. Others will adapt perfectly well to the new feeding situation and could overeat, causing a different imbalance. Spire explains, “Calves will tend to eat what’s in front of them. If we have calves within the group that aren’t eating, that leaves more feed for the calves that are eating. This gives us the chance for some of those calves to overeat and develop subclinical acidosis or full blown acidosis. The signs associated with subclinical acidosis often mimic those of respiratory disease.” In most cases, acidosis does not produce readily observable symptoms, but it’s still enough to affect their intake and the metabolites in their systems. It also can make the calves appear to have respiratory disease, even when the pathogens that cause respiratory disease are not present. It’s important to monitor feed delivery closely the first 2 weeks after the cattle arrive. Review after the first 2 weeks Once the crisis presented by the first 2 weeks has passed, the producer can review the initial vaccination program. Some product labels will indicate that the product should to be followed up with boosters. In those cases, the time between the first and second vaccinations can vary from 3 weeks to 5 or 6 weeks. Spire advises ranchers to follow label directions. “Some vaccines may not give us a long duration of immunity or may need boostering to reach full effectiveness,” he says. “If we don’t follow the recommendation for vaccines we can start seeing some diseases show up a little later, after the first round of vaccines are given.” Among the vaccines presenting a threat from lapsed protection are the clostridials, particularly tetanus, which requires

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2 doses, and BRSV. “Six weeks after we receive the cattle, we can start having issues with BRSV,” Spire says, “so it’s important that we follow the recommendations on the vaccine label and booster the product.” Fall-weaned calf crops, Spire says, don’t tend to present many problems with eyes or feet. There may be some residual problems with some respiratory diseases and clostridials, and parasites could show up, particularly if there hasn’t been a killing frost yet. Spring-weaned calves present different challenges. “After

the initial feeding period we start getting into warm season grasses,” he says, “and we definitely have to emphasize pinkeye control in April and May.” When it’s time to deliver the cattle to the feedlot, provide health records outlining the vaccination program to the feeder. This allows the feedyard manager to know what to look for upon arrival of the calves. Work with your veterinarian to prepare your calves for the next step from the gate to the plate. Your efforts will keep buyers coming back to you for quality beef cattle. ❚

Fall and Early Winter Stocker Cattle Management Proper vaccine boosters and nutrition help stocker cattle fare well in the fall. By Gary DiGiuseppe

Calves have to overcome many traumas including birth, weaning and transportation to grass. While the worst may be over once they’ve become acclimated to a stocker operation, other perils remain. One of those perils is bovine viral diarrhea (BVD). There are 2 major genotypes of the BVD virus in the U.S., categorized as Type 1 and Type 2. Dr. Mark Spire, retired from a career as a technical services manager for Merck Animal Health, explains, “While they’re cousins, they act a little differently in the body. They both can cause mild disease in calves, but the viruses can become very aggressive if the calves are stressed.” That’s because they suppress the animal’s immune system by destroying white blood cells. This is an invitation for all kinds of pathogenic organisms to invade the calf’s body and create a complicated disease problem. One solution is to make sure calves are vaccinated. If you are giving purchased calves their first round of vaccinations at your ranch, make sure the vaccine contains both BVD genotypes. Spire says most calves will respond pretty well. With younger cattle, there are concerns that the dose will be blocked by maternal antibodies still existing in the calf, even though they may be waning. He says, “This serves as the primary vaccination in younger calves at weaning or in newly purchased calves. We can come back and booster our replacement heifers, which gives them good levels of protection. The booster for 12- to 14-month-old thecattlemanmagazine.com

replacement cattle can take them well into the breeding program.” If the stocker operator has a good vaccination program with minimal health risk in a population of calves — and makes the animal health history known to the feedlot — the feedlot operator may decide not to vaccinate upon arrival. If health issues are present though, or if the feedlot has some low level BVD in its operation, it can administer vaccines that act as boosters, not just against BVD but also for other viruses such as infectious bovine rhinotracheitis (IBR), bovine respiratory syncytial virus and PI3. “Our primary vaccination sets the stage for a vaccination program that carries into the wintertime for fall-weaned calves and newly purchased calves coming from wheat pasture or cool-season forage programs,” says Spire. Some locations, particularly the Southeast or areas where it’s very wet, can add lepto to their viral vaccination program. In the vast majority of operations across the U.S., vaccination for clostridial disease should be part of a basic vaccination program. Clostridial and most lepto vaccines are typically followed by a booster within 3 to 6 weeks of the primary dose. Spire says these vaccines are well received by 6- to 8-month-old animals, which develop a high level of protective immunity. Persistently infected calves Many operations screen incoming cattle for being persistently infected with BVD (BVD-PI). Spire says persistently infected calves are the offspring of

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cows that become infected between the first and fourth months of gestation — day 45 to day 125. If the virus doesn’t kill the fetus, the virus replicates as if it were the fetus’ own proteins. The BVD virus is recognized as part of the natural protein in the body, so the calf acts like a Trojan horse and carries the virus for life. The calves then shed vast quantities of the virus through their natural body fluids, infecting their pasture mates. BVD-PI calves are a threat to any cows or replacement heifers that may be running alongside stocker cattle. “Within the 2 types of BVD, we have cytopathogenic and non-cytopathogenic,” Spire says. “The cytopathogenic BVD is really destructive and aggressive. It causes quite a bit of clinical disease. But the non-cytopathogenic BVD is subtle. While it can cause mild disease, it really likes to attack young, developing fetuses.” Pinkeye and parasites There are other concerns for calves arriving at a grazing operation in the fall. Spire says this is right at the end of the pinkeye season, so check calves for pinkeye symptoms and treat them immediately. “Generally, late season vaccination for pinkeye doesn’t give much bang for the buck, so we tend to rely on active treatment programs,” he says. Before the first frost, there is an internal parasite risk. If the calves are dewormed before they go out onto the pasture after the frost, there is very little risk of reinfection. “After deworming, we shift our emphasis toward external parasite control,” he says. “We’ll see lice overwinter on our stocker calves, so we will typically use a product that gets lice and internal parasites at the post-frost treatment period, or we can use a pour-on or an oral feed-through product for internal parasite control. “If the cattle are parasite-clean when they are pulled off of their pastures or forage programs, we’ll have a very responsive calf with a very low health risk going into the feedyard.” Spire also says a good time to remove the old fly tags is while you have the cattle in the squeeze chute for deworming or louse control, rather than leaving the tags on through the winter. During the second and third month after arrival, he suggests that the operator check stocker cattle for major health defects such as eyes injured by pinkeye, swollen and painful joints or feet, or even animals that just aren’t gaining weight. While poor weight gain can be due to a number of reasons, it is most generally from respiratory disease lung damage.

“We can try to salvage those animals and not carry them into the winter, because they just don’t hold up well to environmental extremes,” he says. Maintain high animal health welfare standards and move chronically sick cattle out of the operation. Spire says more feedyards are coordinating with stocker operations, asking them to use specific vaccination programs and treatments. The record prices have had a lot to do with stimulating communications. This can include requests that the calves be dewormed, or that they receive specific boosters, trace minerals or a transition ration. Many in the industry are moving to what he calls “satellite herds” that are owned by the feedyard during the grass phase. He says, “We’re seeing a lot of cattle come in at 900 pounds now, so it’s really important that the feedyard coordinate with their suppliers to have a nice health program set up in advance. That way, they know what health program the cattle are on before they come into the yard.” This helps the feedyards manage their risk of losing a high-priced calf. Proper diet components Diet and its many aspects are obviously crucial to developing stocker cattle. Dr. Dale Blasi, Extension professor and researcher at Kansas State University (KSU), researches the nutrition management of stocker calves. He models his work on research done at Oklahoma State University’s (OSU) old Pawhuska unit, and by Drs. David Hutcheson and Andy Cole at Texas A&M’s station in Amarillo on light-weight, stressed calves and growing programs for stocker cattle. He says, “We take long-hauled stressed calves, predominantly from western Tennessee, and straighten them out for about 45 days. Then we’ll continue a performance study on their growth for another 45 to 70 days.” Their basic growing diet is approximately one-third rolled corn, but Blasi says they’ve had good success using whole shelled corn with lighter weight calves. They also found a good response when wet corn gluten feed was added to the mix. For the forage component, he stresses the importance of keeping the particles coarse enough for good rumen action. “We use about 15 percent alfalfa in our diet,” he says. Forage particles that are too fine can lead to problems in the calves’ digestive systems. At KSU, they tend to feed a higher level of protein in the diet than is called for by the National Research Council. “Protein is a relatively inexpensive ingredient when you’re bringing a

Calves have to overcome many traumas including birth, weaning and transportation to grass. 10 Merck Animal Health BEEF CATTLE PRODUCTION SERIES – PART 3 Weaned Calf and Stocker Cattle Management

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lot of co-product into a diet,” he says. Co-products are those grain products left over from a distillation process. Moisture level in the diet is also important. Blasi believes inclusion of wet co-products adds to a good response by preventing the diet from getting too dry and allowing better blending and composition of the total mixed diet presented to the calves. There are a few other problems to watch for, among them acidosis, but Blasi believes the distillers grains act to settle the rumen. Starchy grain is a more likely cause of this condition, especially if it’s too fine. Coccidiosis is also a concern. “We always utilize Rumensin in our standard diet,” he says. “The Eimeria cocci can get out of control and have an impact on performance and eventually intake. It can really set calves back if you allow that little insidious organism to get a foothold in the digestive tract.” Blasi says calves typically begin gaining weight 7 to 10 days after arrival, and their intake at the start is quite low. This creates the need for fortification with protein and energy. Once they get on full feed, you can start to moderate the amount of

roughage in the diet. He says KSU has just completed a study that found no difference in performance when calves are fed a 30 percent ammoniated wheat straw ration versus plain straw with a wet co-product added for moisture. “The roughage provides for good rumen function but we saw no additional response from the ammoniated wheat straw in the diet,” he says. Spire says once animal health safeguards are put in place, management should be focused on getting the cattle onto a plane of nutrition that will bring them to a target weight by the end of their stay. “If we’ve cleaned the parasites out of them — both internal and external — and we’ve minimized their disease risk, we have a really stable population. The only thing we have to worry about is the effect of major weather events, and we’ll adjust our rations and shelter accordingly for those conditions,” he says. “There’s a pretty minimal health risk issue in late fall and winter for the cattle we brought in earlier in the season.” ❚

Histophilus somnus: Prevalent, Problematic and Hard-to-Diagnose Bacteria By David Bechtol, D.V.M., Palo Duro Consultation, Research & Feedlot, Canyon, Texas, and Dr. Jim Furman, The Animal Center, Alliance, Neb.

Histophilus somni (H. somni) is bacteria capable of infecting the brain, lungs, heart and a variety of joints and tendons. It causes a variety of disease syndromes, such as thrombotic meningoencephalomyelitis (TEME) in the brain, fibrinous pleuritis in the lung, myocarditis/pericarditis in the heart muscle, polysynovitis in the joints and tendons, otitis media (droopy ear), mastitis and reproductive tract diseases. The bacteria is common in the respiratory tract of many normal calves and may not cause any problems at the cowcalf level until after the animal has been exposed to stress such as weaning and/or shipping. Once the animal has been stressed and possibly exposed to a virus, a severe outbreak of bronchopneumonia may occur. The most common clinical syndromes observed in feedlot cattle are respiratory disease, infection of the heart and TEME. It may also be part of the classical “shipping fever complex,” often showing up as a cause of severe fibrinous pleuritis and pericarditis. Other forms of this disease may show up as joint infection and inflammation, causing lameness, or central nervous signs of disease (TEME). Diagnosis is difficult because of the difficulty of culturing at the laboratory. A complete necropsy should be performed upon death as soon as possible. thecattlemanmagazine.com

As an example, a calf dead of central nervous disorder H. somni may have secondary signs of bloat. It is easy for even the experienced veterinarian or pathologist to miss the diagnosis unless the brain, heart and lungs are examined microscopically. The best time for prevention is at the cow-calf level. Because it is a killed bacterial bacterin, it requires 2 vaccinations 2 to 3 weeks apart to have any chance of proper prevention. Some pathologists believe the vaccine in combination with either clostridials or virals is not always effective. However, our experience shows it to be effective when used as a single-antigen vaccine in both the cow-calf and feedlot environment. H. somni is more of a cold weather disease and is seen mostly in the fall when calves are coming into the feedlot. Even though many calves have the organism in their system, it doesn’t seem to show up clinically until the cold weather hits. It is susceptible to a wide variety of antibiotics, and treatment decisions are made according to the veterinarian’s experience with certain drugs. Tetracyclines may be used, as well as many of the newer, longer-acting antibiotics used to treat bovine pneumonia. Early recognition and treatment are very important to the success of response to this organism. ❚

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BRSV: 6 Hours from First Sign to Death By David Bechtol, D.V.M., Palo Duro Consultation, Research & Feedlot, Canyon, Texas

Bovine respiratory syncytial virus (BRSV) primarily causes a lower respiratory tract infection but can set the stage for fatal bacterial pneumonia of cattle. BRSV is a virus that replicates in nasal epithelium before dispersing throughout the upper and lower respiratory tract. It has been implicated as a predisposing factor in fibrinous pneumonia and a cause of interstitial pneumonia. In cases of interstitial pneumonia, in areas of the lung the air sacs expand to bursting and coalesce into 1 large sac. Oxygen is trapped inside the large sac, which has less blood flow to it than each small air sac. The calf eventually will asphyxiate and die. BRSV affects mostly young cattle from 2 to 10 months of age, but can affect yearling and adult cattle. It appears like many other bovine respiratory diseases (BRD), manifesting in a fever often higher than 104 degrees Fahrenheit, depression, decreased feed intake, increased respiratory rate, a harsh cough and a thick nasal discharge. My experience with BRSV has shown fluid-filled, swollen lungs with nasal discharge but no pinkeye (conjunctivitis) that is frequently seen in infectious bovine rhinotracheitis (IBR). Shortness of breath with open-mouth breathing can become pronounced in the later stages of the disease, as well as secondary bacterial infection, increasing the severity. This disease can run its course in less than 6 hours from first clinical signs to death of the animal. Gross lesions often seen by the veterinarian on necropsy include a diffuse interstitial pneumonia along with emphysema and fluid accumulation in the lungs. Secondary bacterial pneumonia is often present as well caused by bacteria not usually associated with acute bacterial pneumonia. A true diagnosis of BRSV requires laboratory confirmation. This virus is difficult to detect because it does not tolerate transport to the lab well. Work with your veterinarian to collect and test tissue samples to confirm a diagnosis. BRSV often starts with comingling of calves at weaning or at the feedyard. Clinical signs tend to show up 7 to 10 days after exposure, which can be by nose-to-nose contact with other sick calves, or through the air; however, I have seen the worst breaks at 21 days after arrival into a feedlot. The number of calves becoming sick can be very high in

an exposed herd, and the episode of disease may have up to 14 to 30 days duration. Due to lack of response of treatment, mortality can be significant, too, possibly up to 20 percent of the group. There is no specific anti-BRSV therapy; therefore, treatment is limited to antibacterial therapy for secondary bacterial infections and supportive treatment. Vaccination is the primary means for control. Modified live virus vaccines have a better track record than killed vaccines. A recently introduced intranasal vaccine appears to give the best protection from this disease and it may be given to calves older than 8 weeks of age. Studies have noted an association between high BRSV serum antibody titers on arrival at the feedlot and a reduced risk of subsequent respiratory disease. The best way to protect vulnerable calves from this disease appears to be vaccinating early and often, because calves as young as 6 weeks of age respond well but protective titers tend to last only a few months. BRSV also seems to be more of a warmer weather disease, exhibiting itself often as a sudden death in the warmer months of the year, particularly in pre-weaned calves at 2 to 6 months of age. Yearling feedyard cattle also seem to be more susceptible during the warmer weather. This can be a difficult disease to control without proper prevention. â?&#x161;

BRSV affects mostly young cattle from 2 to 10 months of age, but can affect yearling and adult cattle. 12 Merck Animal Health BEEF CATTLE PRODUCTION SERIES â&#x20AC;&#x201C; PART 3 Weaned Calf and Stocker Cattle Management

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BVD Causes Multiple Losses to the Cow Herd By David Bechtol, D.V.M., Palo Duro Consultation, Research & Feedlot, Canyon, Texas

Bovine viral diarrhea (BVD) is an important disease for all cattle producers to manage. BVD was first described in 1946 as a severe and often fatal disease in dairy cattle. Early researchers named this disorder ‘mucosal disease’, and many people still call the severe digestive form of BVD by this name. We know this disease can affect other organs, as well as • Cause problems in the digestive tract • Be implicated as a respiratory agent • Cause birth defects • Reduce immuno-suppressive function — weakening the animal’s immune system and lessening its ability to fight other infectious diseases • Affect all ages of cattle • Be found in every segment of beef production BVD is easily transmitted among animals via nasal contact with cow udders or drinkers. Unlike infectious bovine rhinotracheitis (IBR) — which can be spread by nasal contact through drinkers throughout the entire herd in a matter of 3 to 4 days — BVD spreads much more slowly over many weeks, wandering through the herd. There are often no physical signs of infection except for those of other invading agents causing watery eyes, nasal discharge, anorexia, fever and sometimes dehydration with depression. Diarrhea and ulcers of nasal and oral mucosa are other symptoms sometimes accompanying the sickness. The major health risk to the animal from BVD is the secondary opportunist infections occurring because of the suppressed or non-functional immune system. On the ranch, animals that are persistently infected with BVD are feared. These are known as BVD-PI cattle. An animal becomes persistently infected with BVD if • It is from a dam that is persistently infected • If it is from a dam exposed to BVD from day 45 to day 125 of the pregnancy A cow or heifer exposed to BVD during this critical period becomes viremic. The BVD virus circulates in her blood, allowing the virus to flow through the fetal calf’s blood. Since the calf’s immune system is in its development stage from

day 45 to day 125 of gestation, the calf’s immune system will recognize this virus as a part of itself, not as foreign. The calf will probably be aborted and die. If not, the calf may be born weak and then die. Or, it may be born apparently normal and then shed the BVD virus from all secretions of its body — tears, saliva, manure, urine and also milk or semen when it gets older. These calves are thought to be the most dangerous to the producer. They cannot seem to mount any defense against the virus themselves and are always shedding the virus to other animals in the herd. These animals are also at risk of death at any time. Vaccinations play a major role in any herd management program. Consult with your veterinarian to determine if you should use modified live virus (MLV) or killed virus vaccines, in order to avoid problems with pregnant cows or with calves nursing pregnant cows. Losses due to BVD costs the beef industry millions of dollars each year in reduced pregnancy rates, increased abortions and stillbirths, increased death loss prior to weaning and losses to stocker and finishing operations. It is one of the diseases the veterinary profession is working hard to eliminate. Tests are available to eliminate PI and maintain a herd free of BVD-PI cattle. Don’t live with this devastating disease. Develop a program with your veterinarian to protect your livelihood. ❚

BVD is easily transmitted among animals via nasal contact with cow udders or drinkers. 14 Merck Animal Health BEEF CATTLE PRODUCTION SERIES – PART 3 Weaned Calf and Stocker Cattle Management

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