Bovine respiratory disease (BRD) is the most common and costliest problem encountered in stocker or feedlot calves (Griffin, 1997). BRD, also called "shipping fever", causes major economic losses to the producer, 7% of production costs, by reducing average daily gain, feed efficiency, and overall performance of beef calves. The economic loss associated with lower gains and treatment costs for BRD infection in a 1,000-cattle feedlot was estimated as $13.90 per animal (Snowder et al., 2006).
Shipping Fever is a respiratory disease complex that occurs most often within the first month after weaning. The weaning process is a stressful time for calves due to handling, commingling, and shipping to other locations (Blecha et al., 1984). During this period, calves may be exposed to many infectious agents that cause BRD. Stress predisposes calves by affecting their immune system (Galyean and Hubbert, 1995; Cole, 1996). In addition, poor body condition will increase the risk to BRD. As a result, it is possible for calves to develop severe bronchopneumonia and even die from "shipping fever".
Infectious Agents: There are many types of infectious agents involved in this disease complex. The most common viruses involved with BRD include Bovine Viral Diarrhea (BVD), Infectious Bovine Rhinotracheitis (IBR), Bovine Respiratory Synctial Virus (BRSV), and Parainfluenza Type-3 Virus (PI-3) (Plummer et al., 2004). Exposure to these viruses can cause severe damage to the respiratory tract of calves creating opportunities for bacteria to then settle in the lungs. Fortunately, disease caused many of these agents can be prevented through vaccination programs. The most common bacteria found in the lungs of calves with BRD include Mannheimia haemolytica and Pasteurella multocida. Haemophilus somnus may also be involved in cases of pneumonia and can cause severe damage to heart muscles (Pandher et al., 1998; Duff and Galyean, 2007; Griffin et al., 2010). Vaccines are also available for these bacteria. Another bacterial-type organism that is being found more often in the past few years is Mycoplasma bovis (Griffin et al., 2010). This organism not only causes severe pneumonia but also swollen, painful joints in calves. Unfortunately, there is not an effective vaccine or treatment available. It is also possible to find sick calves that have Mycoplasma bovis or are persistently infected (PI) with BVD.
Clinical Signs: Symptoms of BRD usually develop within a month after weaning/marketing (Buhman et al., 2000). Clinical signs can be variable since there may be multiple pathogens involved in this disease complex. Early clinical signs usually include: depression, loss of appetite, and dull eyes (Duff and Gaylean, 2007; Perino and Apley, 1998; Noffsinger and Locatelli, 2004). These calves should be pulled from their group and checked for fever. Temperatures over 104 degrees F indicate early signs of BRD. Clinical signs later in the course of the disease include: rapid/labored breathing, droopy ears, coughing, diarrhea, staggering, nasal discharge or sudden death (Duff and Gaylean, 2007; Bleul, 2009). Because the onset of BRD should be expected after weaning/marketing, producers should closely monitor every calf with quantitative measures such as respiratory rare twice daily for the first few weeks (Perino and Apley, 1998; Noffsinger and Locatelli, 2004). Left untreated, calves with severe BRD will die from their pneumonia and incur economic loss.
Treatment Options: Early recognition and treatment of calves with BRD usually improves their outcome and overall performance (http://www.drovers.com/sites/default/files/ah_beef_04.pdf). Treatment options can vary but most involve use of antibiotics specifically designed to treat calves with pneumonia. Many antibiotics are effective against bacteria most commonly found in the lung tissue. There are new generations of antibiotics which combine effectiveness with less frequent treatments and offer subcutaneous dosing. Some antibiotics have short or no slaughter withdrawal periods. In addition, administration of an anti-inflammatory drug may help reduce fever and damage to the lungs, and may help sick calves get back on feed sooner. Providing calves with 1 gallon of warm water and electrolytes per 100 lbs. of body weight can stimulate appetite and correct the dehydration suffered if the calf is sick for more than 24 hours. Vitamin B and probiotics may also be used to help stimulate appetite (http://pubs.ext.vt.edu/400/400-008/400-008.html). Response to therapy is usually seen within 24 hours, particularly if treatment is initiated early in the course of the disease.
Diagnosis of BRD is usually made on the clinical signs, response to treatment and lung lesions in necropsy. Necropsy on all dead calves is recommended which will help to to confirm the diagnosis of BRD and to find out which pathogens are involved. Necropsy can also provide answers on the nutritional status of the calf and which antibiotics might be most appropriate for treatment (Galyean et al., 1999; Bryant et al. 1999).
Prevention Strategies: Prevention of BRD requires advanced planning and careful attention to herd health management (Duff and Gaylean, 2007). Risks can be reduced by the following steps: (http://pubs.ext.vt.edu/400/400-008/400-008.html; http://www.ag.ndsu.edu/pubs/ansci/beef/as1154w.htm)
• Good nutrition before weaning,
• Reducing stresses related to handling and shipping,
• Purchasing source-verified cattle from herds with a known health history,
• Vaccinating calves pre-weaning followed by booster vaccinations at weaning,
• Vaccinating calves at processing
• Castrating and weaning calves and allowing them time to acclimate to eating from a bunk prior to shipment is also a good idea
• Treating any calves that appear sick or have a fever as soon as possible
Mass medication (metaphylaxis) with long acting antibiotics given to all calves on arrival, is another common prevention strategy (Loffgreen, 1983; Nickel and White, 2010) to reduce the number of BRD cases in calves on arrival. Treated calves will have better average daily gain, feed efficiency, and overall performance. These factors support the use of metaphylaxis and have proven to be cost effective.
Some factors to consider when deciding to mass medicate are:
• Source of the calves as well as that of your own farm should be considered.
• Calves are more likely to get sick in the fall than any other time of the year.
• Inclement weather probably plays the single largest role in the likelihood of a large number of calves becoming sick.
• Calves that are not weaned when marketed are much more likely to get sick.
• Calves weighing • Calves castrated after marketing are more likely to contract BRD.
Bovine Respiratory Disease is economically important disease. Consult your veterinarians for effective vaccination strategies and management and treatment options. Your veterinarians will consider age and source of the animal, the type of stress the animal will tolerate, laboratory antibiotic sensitivities for isolated bacterial pathogens, the withdrawal time so that no violative residues will be found and most importantly available for the follow-up. Cattlemen must understand it is a violation of federal law to use antibiotics other than as directed on the label unless prescribed by a veterinarian.
Source: Dr. Ram Kasimanickam, Washington State University Extension
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