- Email: [email protected]
Investigating Feedlot Respiratory Disease Outbreaks
CHAPTER 128 5. Lubbers BV, Apley M: A case of papillomatous digital dermatitis in feedyard cattle, St Paul, Minn, 116-118, 2006, Proceedings American Association of Bovine Practitioners 39th Annual Convention. 6. Brent BE: Relationship of acidosis to other feedlot ailments, J Anim Sci 43:930-935, 1976. 7. Bergsten C: Causes, risk factors, and prevention of laminitis and related claw lesions, Acta Vet Scand Suppl 98:157-166, 2003. 8. Adegboye DS, Halbur PG, Nutsch RG et al: Mycoplasma bovis–associated pneumonia and arthritis complicated with pyogranulomatous tenosynovitis in calves, J Am Vet Med Assoc 209:647-649, 1996.
CHAPTER
Investigating Feedlot Respiratory Disease Outbreaks
673
9. Guard C: Super foot rot. In Howard JL, Smith RA, editors: Current veterinary therapy IV: food animal practice, Philadelphia, 1999, Saunders, pp 693-694. 10. Grandin T: Handling methods and facilities to reduce stress on cattle, Vet Clin North Am Food Anim Pract 14:325-341, 1998. 11. O’Toole D, Steadman L, Raisbeck M et al: Myositis, lameness, and recumbency after use of water-in-oil adjuvanted vaccines in near-term beef cattle, J Vet Diagn Invest 17:23-31, 2005. 12. Feedlot ‘99 part I: baseline reference of feedlot management practices (website): http://www.nahms.aphis.usda.gov/feedlot/ feedlot99/FD99Pt1.pdf.
128
Investigating Feedlot Respiratory Disease Outbreaks LARRY C. HOLLIS
R
espiratory disease in feedlot cattle is a common occurrence. In the most recent National Animal Health Monitoring Service (NAHMS) report, more than 14% of all cattle entering the feedlot were reportedly treated for respiratory disease.1 The majority of bovine respiratory disease (BRD) problems are anticipated to occur within the first 30 days after arrival at the feedlot, usually as a sequela to the combination of events that occurred in the life of the animal shortly before and/or after arrival at the feedlot. The stresses of weaning; transitioning to and through the marketing channels; commingling; transportation to the feedlot; changing environment (not just from pasture to drylot conditions, but often including changes in range of daily temperature, humidity, solar radiation, wind exposure, dust, freezing rain or snow, elevation, etc.); being processed with a variety of vaccines, a parasiticide, an implant, and ear tag; possibly being castrated, dehorned, and branded; adapting to different feed types and water sources; establishing a new social order with unknown penmates; and dealing with a variety of strange vehicles and strange people on even stranger creatures called horses contribute to the development of physiologic changes within cattle. This stress allows previously innocuous bacterial inhabitants of the upper nasal cavity to proliferate, migrate to the lower respiratory tract, and cause disease in individual animals. This series of events is familiar to experienced feedlot
operations, and the resultant BRD is normally anticipated once all risk factors are taken into consideration. The problem arises when BRD occurs at an unexpectedly high rate or an unexpected time during the feeding period, or when treatment failures occur. When any of these situations arise, they can lead to great consternation and present a management crisis that sometimes leads to accusations and finger pointing. Where cooler heads prevail, they are the cause for critical investigation to determine (1) what is happening, (2) why is it happening, (3) what steps can be undertaken to correct the current situation, and (4) what can be done to prevent a similar recurrence in future groups of feeder cattle. Investigating a feedlot respiratory disease outbreak is a process of looking through a series of potentially contributing or controlling factors. If one moves through the investigation in a stepwise fashion, it may help prevent overlooking some important piece(s) of information.
BE PREPARED Preparation for investigating a respiratory disease outbreak actually occurs well before the initial crisis arises. The veterinarian should have an established working relationship with a veterinary diagnostic laboratory and be familiar with personnel, testing capabilities, sampling requirements, and normal turnaround time for samples
674
CHAPTER 128
Investigating Feedlot Respiratory Disease Outbreaks
submitted to the laboratory. The laboratory can serve as a vital resource, not only to perform the tests, but also as a source of well-educated colleagues to help brainstorm the situation. Having an established line of communication with appropriate laboratory personnel and incorporating them as diagnostic consultants can sometimes help in making sure appropriate tests and specialized handling requirements are considered, and it may even speed up the priority or rate of sample processing once samples reach the laboratory. The next step is to have the equipment and supplies on hand that might be necessary in any disease investigation. Items such as necropsy equipment, sample collection supplies such as Whirl-Paks, 10% neutral buffered formalin, vacutainer tubes, blood collection equipment, tracheal or deep nasal swabs, tracheal wash supplies, special culture or transport media (viral and bacterial [anaerobic and aerobic]), pH strips, urine ketone and glucose strips, cooler and ice packs, and shipping containers are often vital to the success of any field disease investigation. Both digital still and video cameras may prove useful to document situations, lesions, or clinical signs, especially if they are unique.
GATHER THE PERTINENT HISTORY The initial contact by feedlot personnel will describe the reason for their concern. As information about the cattle and situation is put together, a mental picture will begin to develop. Questions should move from general to specific. The normal starting point is a series of general questions, usually starting with asking about the region of the country where the cattle originated. The experienced feedlot veterinarian knows that a semiload of cattle purchased through an order buyer in a particular state may be made up of cattle originating from up to 40 different farms located in 10 different states. The “origin” just happens to be the home base for the order buyer who assembled the load. Gathering this type of history helps the veterinarian determine that the cattle may have come from an area where cattle are commonly mismanaged or undermanaged, a mineral-deficient area, an area where tall fescue frequently creates a toxicity problem, or where internal or external parasitism may be a major contributing factor. Specific history of the cattle should be obtained. What is the age, sex, quality, and origin of the cattle? How were the cattle purchased or supplied to the feedlot—ranch/ farm of origin, video auction, local auction barn, stocker or backgrounding operation, order buyer? If cattle were from multiple origins, how long did it take to put the load together? From which states were cattle assembled? Were cattle fresh at the time of purchase? Were cattle preconditioned? What products, procedures, and timing were included in any preconditioning program? Was anything requested to be done to cattle at an order buyer facility (e.g., castrated, dehorned, vaccinated, mass medicated, individuals treated for illness)? Were any things done that were not requested or anticipated before shipment? Were the trucks clean before the cattle were loaded? When did the trucks load up and leave for the feedlot? What was the distance between the origin and the feedlot? How long
were the trucks en route? Did the trucks encounter any delays? Answers to these questions help develop the mental picture further and provide additional insight into the overall situation. Arrival history at the feedlot should then be obtained. What time of day/night did the trucks arrive? Did a qualified person watch the cattle unload from the trucks? Did the cattle match the description of the order from a health status and freshness appearance, as well as number, sex, quality, etc.? Were there dead cattle on the truck or cattle that were obviously sick as they unloaded from the truck? What did the cattle do when they were placed in the receiving pen—explore the pen, search for feed and water, or lay down and rest? Did the cattle appear dehydrated? Were the cattle bawling? How much did the cattle shrink from payweight at the point of origin to the inweight at the feedlot? Were answers based on memory, or were these items routinely recorded for each set of cattle received at the feedlot? Again, answers to these questions provide additional insight. Processing history should be obtained next. How long were the cattle rested between arrival at the feedlot and processing? Were backtags removed to see if the amount of hair retained on the backtag matched the amount of hair missing from the spot where the backtag was removed? Which vaccines were administered and what procedures were conducted during processing? How were the vaccines handled from the time of purchase until the actual time of administration to the animals? Were observations made for sick cattle before and during processing? Were temperatures taken as animals were being processed? Were any delays encountered during processing? Were cattle mass medicated and, if so, with what product and dose? Has the processing crew experienced problems in the past? Were new personnel working on the processing crew the day the problem cattle were processed? Were serial numbers recorded for products administered, as well as the name of the individual administering each product? Were answers based on memory, or were these items routinely recorded for each set of cattle processed at the feedlot? All of these answers lead to more insight. Transitioning to feed history should be obtained. What is the general history of this feedlot’s ability to mix rations properly and deliver the correct ration to the correct pen of cattle on a timely basis? Were there any problems getting the cattle started on feed? How does this feedlot transition cattle from starting ration to finishing ration? Which ration step were the cattle on when the respiratory outbreak started? If the problem occurred later in the feeding period, were there any problems getting the cattle to step up through the intermediate rations to the top ration? Were there any feed-related problems at any time before the time the respiratory outbreak occurred? Time and location history should be obtained. Is there only a single pen or several groups of cattle affected? Is it a generalized problem or localized to a specific area within the feedlot? Is there a pattern in the age, sex, or arrival time of affected cattle? Is the affected section of the feedlot served by a specific treatment facility? Did the problem arise following a weekend, holiday, or major social event when feedlot employees might have been preoccupied? Are there new pen riders or new members
CHAPTER 128 of the treatment crew? How well do they know their jobs? Has the veterinarian observed them doing their jobs?
STOP, LOOK, and LISTEN An onsite visit is always desirable and often required to determine what is happening. Unless a veterinarian has trained the people he or she is talking to and knows their capabilities and limitations, he or she should resist the temptation to try to diagnose the situation by long distance. Most well-trained feedlot personnel are honest with themselves and know when they are seeing something out of the ordinary. However, they sometimes panic if they are surprised by an unexpected outbreak. The veterinarian should listen to what they have to say, then go look for himself or herself. What one hears over the phone and what one encounters in person are sometimes different. The veterinarian should observe the cattle in question. He or she should look at the remaining cattle in the problem pen(s), first from a distance, then walk through the pen to look at individual animals and pen conditions, listen for abnormal respiratory sounds, and check for abnormal odors. If the veterinarian has trouble seeing the problem, he or she can have the pen rider show which animals fit the problem encountered or explain what was observed. Next, the veterinarian should look at problem cattle in the sick pen or hospital area, looking and listening to cattle that are currently being treated. He or she should check the treatment records, looking especially at recorded temperatures and to determine if the recommended treatment regimen is being followed. The lungs of typically affected animals should be auscultated. The veterinarian should talk to the people: the processing crew, pen riders, treatment crew, feed truck drivers, and others who work directly with the cattle. This should not be done in the presence of management personnel. Ask them what they noticed. One may be surprised what can be learned from the lowest-paid employee on the feedlot.
SAMPLING The veterinarian should sample live animals. The preferable animals for sample collection are acutely affected, recently selected live animals exhibiting typical symptoms of the respiratory disease problem in question. Samples should be collected before any antibacterial or symptomatic therapy. When collecting samples for culture purposes, laryngeal swabs or tracheal washes often provide samples with fewer contaminants than deep nasal swabs, which in turn have fewer contaminants that shallow nasal swabs. Blood for virus isolation and serology and other body fluids should be collected at this time. Unneeded samples can always be thrown away later. The veterinarian should necropsy dead animals. The ideal animal to collect necropsy samples from would be an untreated animal that died shortly before the necropsy; however, any dead animal from the problem group will have a story to tell. Perform a complete necropsy, looking for any lesions or indicators of problems in other body systems that may have contributed to
Investigating Feedlot Respiratory Disease Outbreaks
675
the respiratory problem observed (e.g., systemic salmonellosis, Histophilus somni lesions in heart or brain). Observe the entire respiratory tract including nasal passages, trachea, and lungs. Observe the pattern of changes in the lungs including the color, weight, texture, and lobes affected. Check for the presence of verminous pneumonia. Collect a complete set of fresh tissue samples for bacterial and viral culture and formalin-fixed tissues for histopathology. Collect and retain samples of any abnormal fluids. Samples should be submitted to the diagnostic laboratory in a timely fashion, which often means being handcarried to the laboratory on the day of collection. If in doubt, and fresh dead cattle are available, the veterinarian may want to send one or several intact animals to the laboratory for necropsy.
WHEN THINGS DO NOT ADD UP When things a veterinarian is seeing do not add up mentally, he or she should dig deeper. Several consulting veterinarians have encountered situations where processing or treatment records were being falsely completed by feedlot personnel to cover up the theft of biologic or pharmaceutic products from the feedlot. When these products were diverted from use in the cattle, disease outbreaks or “treatment” failures occurred. Keeping products under lock and key, recording the serial numbers, checking these products out to the processing and treatment crews, and requiring them to check the empty bottles or containers back into the office where the serial numbers were rechecked, caused theft to go down and respiratory (and other) disease problems to improve. In a somewhat similar situation, treatment records were being falsified to cover up the fact that the person in charge of treating sick cattle did not like the consultant’s treatment regimen and chose instead to use his own favorite program. Because the individual “dry labbed” treatment records to indicate he was following the consultant’s recommendations, his paperwork always looked correct. Reconciling product inventories against reported use and hiring an undercover agent to work with the treatment crew and document the falsified records were tools used to determine the reason behind the treatment failures experienced in this case.2 In another situation, a feedlot had been experiencing an unusually high frequency of injection-site abscesses. Feedlot management told the processing crew to clean up the problem, but gave no specific directions for how it was to be accomplished. Shortly thereafter, the feedlot started experiencing problems that were thought to be a vaccine failure caused by a series of laboratory-diagnosed infectious bovine rhinotracheitis (IBR) problems. When feedlot records were evaluated, the problem was not consistent across all pens processed with the same vaccine. When the sequence of processing was evaluated, it became obvious that pens of cattle processed early in the day were not having any IBR problems. Pens of cattle processed later in the day experiencing an increasing percentage of IBR problems directly correlated to the lateness of the hour when they were processed. When the entire processing procedure was observed, the cause became apparent. The crew had realized that their sanitation problems became
676
CHAPTER 128
Investigating Feedlot Respiratory Disease Outbreaks
steadily worse as the day progressed. As one potential solution, they decided to mix all modified live vaccines at the start of the day when everything was clean to prevent possible contamination during mixing later in the day. The vaccine obviously became more inactivated as the day grew longer. Changing their reconstitution procedures solved the IBR problem.3 In a different type of situation, a pen rider was making additional money by training horses for other people and riding them in the feedlot as he did his daily job. Management started noticing spikes in respiratory death losses in pens he was checking. Closer consideration suggested that these spikes correlated to the time when he started working with each new horse. Closer observation of this individual’s work routine revealed that he initially spent more time in the pen teaching each new horse to rein than he did looking for sick cattle. His horseback activities would actually stir up the cattle in the pen, interfering with his ability to identify sick cattle when he finally started looking for them. Discontinuing the practice of
CHAPTER
allowing non–employee-owned horses in the feedlot stopped these spikes in death loss.
CONCLUSION Investigating respiratory disease outbreaks in the feedlot takes preparation, planning, training, an inquisitive mind, a systematic approach, and perseverance. It takes an understanding of both the science and management factors associated with respiratory disease. And, sometimes, it takes a little luck.
References
1. National Animal Health Monitoring System: Health management and biosecurity in U.S. feedlots, Feedlot ‘99 Part III:22, 2000. 2. Miles DG: Personal communication, circa 1989. 3. Hill WJ: Personal communication, circa 1985.
129
Feedlot Therapeutic Protocols MICHAEL D. APLEY
W
ritten protocols are essential to achieve consistent and accurate application of therapy for diseases commonly encountered in feedlots. This section addresses the structure of feedlot therapeutic protocols. Protocol sophistication varies depending on the autonomy of the individuals treating cattle. Regardless of how extensive a protocol is, it is important that all of the people who will be using it have ownership in developing the contents, monitoring results, and updating the protocol. In addition to benefits to the production facility, detailed protocols and records of education and agreement related to the protocols are important to the veterinarian in the case of a violative drug residue or regulatory inspection. A complete protocol should include the following diseases. • R espiratory disease • L ow risk (expected morbidity = 10%, case fatality 1%-2%) • High risk (expected morbidity > 10%, case fatality > 2% up to 10%)
• • • •
• Heavy cattle within 30 days of harvest (withdrawal times are now a primary consideration) • Acute interstitial pneumonia (AIP) • Tracheal edema (Honkers) • Diphtheria (relatively rare in the feedlot) Gastrointestinal disease • Acidosis • Bloat • Coccidiosis Musculoskeletal disease • Footrot • Sole abscesses • Undifferentiated lameness (e.g., sprains) • Hairy heel wart (Strawberry footrot) Central nervous system disease • Polioencephalomalacia • Thrombolic meningoencephalitis • Listeriosis Miscellaneous • Rectal, vaginal, and uterine prolapses • Calvers and abortions • Anaphylactic shock
CHAPTER
Investigating Feedlot Respiratory Disease Outbreaks
673
9. Guard C: Super foot rot. In Howard JL, Smith RA, editors: Current veterinary therapy IV: food animal practice, Philadelphia, 1999, Saunders, pp 693-694. 10. Grandin T: Handling methods and facilities to reduce stress on cattle, Vet Clin North Am Food Anim Pract 14:325-341, 1998. 11. O’Toole D, Steadman L, Raisbeck M et al: Myositis, lameness, and recumbency after use of water-in-oil adjuvanted vaccines in near-term beef cattle, J Vet Diagn Invest 17:23-31, 2005. 12. Feedlot ‘99 part I: baseline reference of feedlot management practices (website): http://www.nahms.aphis.usda.gov/feedlot/ feedlot99/FD99Pt1.pdf.
128
Investigating Feedlot Respiratory Disease Outbreaks LARRY C. HOLLIS
R
espiratory disease in feedlot cattle is a common occurrence. In the most recent National Animal Health Monitoring Service (NAHMS) report, more than 14% of all cattle entering the feedlot were reportedly treated for respiratory disease.1 The majority of bovine respiratory disease (BRD) problems are anticipated to occur within the first 30 days after arrival at the feedlot, usually as a sequela to the combination of events that occurred in the life of the animal shortly before and/or after arrival at the feedlot. The stresses of weaning; transitioning to and through the marketing channels; commingling; transportation to the feedlot; changing environment (not just from pasture to drylot conditions, but often including changes in range of daily temperature, humidity, solar radiation, wind exposure, dust, freezing rain or snow, elevation, etc.); being processed with a variety of vaccines, a parasiticide, an implant, and ear tag; possibly being castrated, dehorned, and branded; adapting to different feed types and water sources; establishing a new social order with unknown penmates; and dealing with a variety of strange vehicles and strange people on even stranger creatures called horses contribute to the development of physiologic changes within cattle. This stress allows previously innocuous bacterial inhabitants of the upper nasal cavity to proliferate, migrate to the lower respiratory tract, and cause disease in individual animals. This series of events is familiar to experienced feedlot
operations, and the resultant BRD is normally anticipated once all risk factors are taken into consideration. The problem arises when BRD occurs at an unexpectedly high rate or an unexpected time during the feeding period, or when treatment failures occur. When any of these situations arise, they can lead to great consternation and present a management crisis that sometimes leads to accusations and finger pointing. Where cooler heads prevail, they are the cause for critical investigation to determine (1) what is happening, (2) why is it happening, (3) what steps can be undertaken to correct the current situation, and (4) what can be done to prevent a similar recurrence in future groups of feeder cattle. Investigating a feedlot respiratory disease outbreak is a process of looking through a series of potentially contributing or controlling factors. If one moves through the investigation in a stepwise fashion, it may help prevent overlooking some important piece(s) of information.
BE PREPARED Preparation for investigating a respiratory disease outbreak actually occurs well before the initial crisis arises. The veterinarian should have an established working relationship with a veterinary diagnostic laboratory and be familiar with personnel, testing capabilities, sampling requirements, and normal turnaround time for samples
674
CHAPTER 128
Investigating Feedlot Respiratory Disease Outbreaks
submitted to the laboratory. The laboratory can serve as a vital resource, not only to perform the tests, but also as a source of well-educated colleagues to help brainstorm the situation. Having an established line of communication with appropriate laboratory personnel and incorporating them as diagnostic consultants can sometimes help in making sure appropriate tests and specialized handling requirements are considered, and it may even speed up the priority or rate of sample processing once samples reach the laboratory. The next step is to have the equipment and supplies on hand that might be necessary in any disease investigation. Items such as necropsy equipment, sample collection supplies such as Whirl-Paks, 10% neutral buffered formalin, vacutainer tubes, blood collection equipment, tracheal or deep nasal swabs, tracheal wash supplies, special culture or transport media (viral and bacterial [anaerobic and aerobic]), pH strips, urine ketone and glucose strips, cooler and ice packs, and shipping containers are often vital to the success of any field disease investigation. Both digital still and video cameras may prove useful to document situations, lesions, or clinical signs, especially if they are unique.
GATHER THE PERTINENT HISTORY The initial contact by feedlot personnel will describe the reason for their concern. As information about the cattle and situation is put together, a mental picture will begin to develop. Questions should move from general to specific. The normal starting point is a series of general questions, usually starting with asking about the region of the country where the cattle originated. The experienced feedlot veterinarian knows that a semiload of cattle purchased through an order buyer in a particular state may be made up of cattle originating from up to 40 different farms located in 10 different states. The “origin” just happens to be the home base for the order buyer who assembled the load. Gathering this type of history helps the veterinarian determine that the cattle may have come from an area where cattle are commonly mismanaged or undermanaged, a mineral-deficient area, an area where tall fescue frequently creates a toxicity problem, or where internal or external parasitism may be a major contributing factor. Specific history of the cattle should be obtained. What is the age, sex, quality, and origin of the cattle? How were the cattle purchased or supplied to the feedlot—ranch/ farm of origin, video auction, local auction barn, stocker or backgrounding operation, order buyer? If cattle were from multiple origins, how long did it take to put the load together? From which states were cattle assembled? Were cattle fresh at the time of purchase? Were cattle preconditioned? What products, procedures, and timing were included in any preconditioning program? Was anything requested to be done to cattle at an order buyer facility (e.g., castrated, dehorned, vaccinated, mass medicated, individuals treated for illness)? Were any things done that were not requested or anticipated before shipment? Were the trucks clean before the cattle were loaded? When did the trucks load up and leave for the feedlot? What was the distance between the origin and the feedlot? How long
were the trucks en route? Did the trucks encounter any delays? Answers to these questions help develop the mental picture further and provide additional insight into the overall situation. Arrival history at the feedlot should then be obtained. What time of day/night did the trucks arrive? Did a qualified person watch the cattle unload from the trucks? Did the cattle match the description of the order from a health status and freshness appearance, as well as number, sex, quality, etc.? Were there dead cattle on the truck or cattle that were obviously sick as they unloaded from the truck? What did the cattle do when they were placed in the receiving pen—explore the pen, search for feed and water, or lay down and rest? Did the cattle appear dehydrated? Were the cattle bawling? How much did the cattle shrink from payweight at the point of origin to the inweight at the feedlot? Were answers based on memory, or were these items routinely recorded for each set of cattle received at the feedlot? Again, answers to these questions provide additional insight. Processing history should be obtained next. How long were the cattle rested between arrival at the feedlot and processing? Were backtags removed to see if the amount of hair retained on the backtag matched the amount of hair missing from the spot where the backtag was removed? Which vaccines were administered and what procedures were conducted during processing? How were the vaccines handled from the time of purchase until the actual time of administration to the animals? Were observations made for sick cattle before and during processing? Were temperatures taken as animals were being processed? Were any delays encountered during processing? Were cattle mass medicated and, if so, with what product and dose? Has the processing crew experienced problems in the past? Were new personnel working on the processing crew the day the problem cattle were processed? Were serial numbers recorded for products administered, as well as the name of the individual administering each product? Were answers based on memory, or were these items routinely recorded for each set of cattle processed at the feedlot? All of these answers lead to more insight. Transitioning to feed history should be obtained. What is the general history of this feedlot’s ability to mix rations properly and deliver the correct ration to the correct pen of cattle on a timely basis? Were there any problems getting the cattle started on feed? How does this feedlot transition cattle from starting ration to finishing ration? Which ration step were the cattle on when the respiratory outbreak started? If the problem occurred later in the feeding period, were there any problems getting the cattle to step up through the intermediate rations to the top ration? Were there any feed-related problems at any time before the time the respiratory outbreak occurred? Time and location history should be obtained. Is there only a single pen or several groups of cattle affected? Is it a generalized problem or localized to a specific area within the feedlot? Is there a pattern in the age, sex, or arrival time of affected cattle? Is the affected section of the feedlot served by a specific treatment facility? Did the problem arise following a weekend, holiday, or major social event when feedlot employees might have been preoccupied? Are there new pen riders or new members
CHAPTER 128 of the treatment crew? How well do they know their jobs? Has the veterinarian observed them doing their jobs?
STOP, LOOK, and LISTEN An onsite visit is always desirable and often required to determine what is happening. Unless a veterinarian has trained the people he or she is talking to and knows their capabilities and limitations, he or she should resist the temptation to try to diagnose the situation by long distance. Most well-trained feedlot personnel are honest with themselves and know when they are seeing something out of the ordinary. However, they sometimes panic if they are surprised by an unexpected outbreak. The veterinarian should listen to what they have to say, then go look for himself or herself. What one hears over the phone and what one encounters in person are sometimes different. The veterinarian should observe the cattle in question. He or she should look at the remaining cattle in the problem pen(s), first from a distance, then walk through the pen to look at individual animals and pen conditions, listen for abnormal respiratory sounds, and check for abnormal odors. If the veterinarian has trouble seeing the problem, he or she can have the pen rider show which animals fit the problem encountered or explain what was observed. Next, the veterinarian should look at problem cattle in the sick pen or hospital area, looking and listening to cattle that are currently being treated. He or she should check the treatment records, looking especially at recorded temperatures and to determine if the recommended treatment regimen is being followed. The lungs of typically affected animals should be auscultated. The veterinarian should talk to the people: the processing crew, pen riders, treatment crew, feed truck drivers, and others who work directly with the cattle. This should not be done in the presence of management personnel. Ask them what they noticed. One may be surprised what can be learned from the lowest-paid employee on the feedlot.
SAMPLING The veterinarian should sample live animals. The preferable animals for sample collection are acutely affected, recently selected live animals exhibiting typical symptoms of the respiratory disease problem in question. Samples should be collected before any antibacterial or symptomatic therapy. When collecting samples for culture purposes, laryngeal swabs or tracheal washes often provide samples with fewer contaminants than deep nasal swabs, which in turn have fewer contaminants that shallow nasal swabs. Blood for virus isolation and serology and other body fluids should be collected at this time. Unneeded samples can always be thrown away later. The veterinarian should necropsy dead animals. The ideal animal to collect necropsy samples from would be an untreated animal that died shortly before the necropsy; however, any dead animal from the problem group will have a story to tell. Perform a complete necropsy, looking for any lesions or indicators of problems in other body systems that may have contributed to
Investigating Feedlot Respiratory Disease Outbreaks
675
the respiratory problem observed (e.g., systemic salmonellosis, Histophilus somni lesions in heart or brain). Observe the entire respiratory tract including nasal passages, trachea, and lungs. Observe the pattern of changes in the lungs including the color, weight, texture, and lobes affected. Check for the presence of verminous pneumonia. Collect a complete set of fresh tissue samples for bacterial and viral culture and formalin-fixed tissues for histopathology. Collect and retain samples of any abnormal fluids. Samples should be submitted to the diagnostic laboratory in a timely fashion, which often means being handcarried to the laboratory on the day of collection. If in doubt, and fresh dead cattle are available, the veterinarian may want to send one or several intact animals to the laboratory for necropsy.
WHEN THINGS DO NOT ADD UP When things a veterinarian is seeing do not add up mentally, he or she should dig deeper. Several consulting veterinarians have encountered situations where processing or treatment records were being falsely completed by feedlot personnel to cover up the theft of biologic or pharmaceutic products from the feedlot. When these products were diverted from use in the cattle, disease outbreaks or “treatment” failures occurred. Keeping products under lock and key, recording the serial numbers, checking these products out to the processing and treatment crews, and requiring them to check the empty bottles or containers back into the office where the serial numbers were rechecked, caused theft to go down and respiratory (and other) disease problems to improve. In a somewhat similar situation, treatment records were being falsified to cover up the fact that the person in charge of treating sick cattle did not like the consultant’s treatment regimen and chose instead to use his own favorite program. Because the individual “dry labbed” treatment records to indicate he was following the consultant’s recommendations, his paperwork always looked correct. Reconciling product inventories against reported use and hiring an undercover agent to work with the treatment crew and document the falsified records were tools used to determine the reason behind the treatment failures experienced in this case.2 In another situation, a feedlot had been experiencing an unusually high frequency of injection-site abscesses. Feedlot management told the processing crew to clean up the problem, but gave no specific directions for how it was to be accomplished. Shortly thereafter, the feedlot started experiencing problems that were thought to be a vaccine failure caused by a series of laboratory-diagnosed infectious bovine rhinotracheitis (IBR) problems. When feedlot records were evaluated, the problem was not consistent across all pens processed with the same vaccine. When the sequence of processing was evaluated, it became obvious that pens of cattle processed early in the day were not having any IBR problems. Pens of cattle processed later in the day experiencing an increasing percentage of IBR problems directly correlated to the lateness of the hour when they were processed. When the entire processing procedure was observed, the cause became apparent. The crew had realized that their sanitation problems became
676
CHAPTER 128
Investigating Feedlot Respiratory Disease Outbreaks
steadily worse as the day progressed. As one potential solution, they decided to mix all modified live vaccines at the start of the day when everything was clean to prevent possible contamination during mixing later in the day. The vaccine obviously became more inactivated as the day grew longer. Changing their reconstitution procedures solved the IBR problem.3 In a different type of situation, a pen rider was making additional money by training horses for other people and riding them in the feedlot as he did his daily job. Management started noticing spikes in respiratory death losses in pens he was checking. Closer consideration suggested that these spikes correlated to the time when he started working with each new horse. Closer observation of this individual’s work routine revealed that he initially spent more time in the pen teaching each new horse to rein than he did looking for sick cattle. His horseback activities would actually stir up the cattle in the pen, interfering with his ability to identify sick cattle when he finally started looking for them. Discontinuing the practice of
CHAPTER
allowing non–employee-owned horses in the feedlot stopped these spikes in death loss.
CONCLUSION Investigating respiratory disease outbreaks in the feedlot takes preparation, planning, training, an inquisitive mind, a systematic approach, and perseverance. It takes an understanding of both the science and management factors associated with respiratory disease. And, sometimes, it takes a little luck.
References
1. National Animal Health Monitoring System: Health management and biosecurity in U.S. feedlots, Feedlot ‘99 Part III:22, 2000. 2. Miles DG: Personal communication, circa 1989. 3. Hill WJ: Personal communication, circa 1985.
129
Feedlot Therapeutic Protocols MICHAEL D. APLEY
W
ritten protocols are essential to achieve consistent and accurate application of therapy for diseases commonly encountered in feedlots. This section addresses the structure of feedlot therapeutic protocols. Protocol sophistication varies depending on the autonomy of the individuals treating cattle. Regardless of how extensive a protocol is, it is important that all of the people who will be using it have ownership in developing the contents, monitoring results, and updating the protocol. In addition to benefits to the production facility, detailed protocols and records of education and agreement related to the protocols are important to the veterinarian in the case of a violative drug residue or regulatory inspection. A complete protocol should include the following diseases. • R espiratory disease • L ow risk (expected morbidity = 10%, case fatality 1%-2%) • High risk (expected morbidity > 10%, case fatality > 2% up to 10%)
• • • •
• Heavy cattle within 30 days of harvest (withdrawal times are now a primary consideration) • Acute interstitial pneumonia (AIP) • Tracheal edema (Honkers) • Diphtheria (relatively rare in the feedlot) Gastrointestinal disease • Acidosis • Bloat • Coccidiosis Musculoskeletal disease • Footrot • Sole abscesses • Undifferentiated lameness (e.g., sprains) • Hairy heel wart (Strawberry footrot) Central nervous system disease • Polioencephalomalacia • Thrombolic meningoencephalitis • Listeriosis Miscellaneous • Rectal, vaginal, and uterine prolapses • Calvers and abortions • Anaphylactic shock