Bovine respiratory disease (BRD) is the most common and costly problem encountered in stocker or feedlot calves. BRD, also called “shipping fever”, also accounts for major economic losses to the producer by reducing average daily gain, feed efficiency, and overall performance of beef calves. The primary objective of this chapter is to further explain the mechanisms, clinical signs, and treatment of BRD. More importantly, prevention of BRD as the primary objective in a herd health management plan will be emphasized.
What is BRD?
BRD is a respiratory disease complex that occurs most often within 14 days after calves have been weaned. The weaning process is the most stressful time for calves. At that time, calves are usually castrated, extensively handled, commingled, and shipped to other locations. During this period of time, calves will have tremendous exposure to the many infectious agents that cause BRD. Stress will also have a negative impact on the immune system of calves causing them to be even more vulnerable to “shipping fever”. Other factors which increase their level of risk to BRD is movement thru sale yards, poor body condition, and transport over long distances. On arrival at final destinations, calves are often dehydrated, exhausted, and have a reduction in appetite. Many calves are vulnerable to being in the early stages of BRD. As a result, it is not uncommon for many calves to develop severe bronchopneumonia and even die from “shipping fever”.
What Infectious Agents are Involved with BRD?
There are several types of infectious agents involved causing the calf to become vulnerable to this complex respiratory disease. Fortunately, many of these agents can now be prevented through vaccination programs. 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). Exposure to these virus can cause severe damage to the airways (respiratory tract) of calves creating opportunities for bacteria to then settle in the lungs.
The most common bacteria found in the lungs of calves with BRD include Mannheimia haemolytica and Pasteurella multocida. Haemophilus somnus may also be involved and often causes severe damage to the heart muscles. Vaccines are also available for these bacteria. Another bacteria-type organism that is being found more often in the past few years is Mycoplasma bovis. 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 not uncommon to find sick calves that have Mycoplasma bovis and are persistently infected (PI) with BVD.
What are the Clinical Signs of BRD?
Symptoms of BRD usually develop within 14 days after the weaning process. Signs can be variable since there may be one or more viruses and bacteria involved in this disease complex. Early clinical signs usually include: depression, anorexia, and dull eyes. These calves should be immediately pulled and checked for fever. Temperatures over 104 degrees indicate early signs of BRD! Clinical signs later in the course of the disease include: rapid/labored breathing, droopy ears, coughing, diarrhea, sudden death, staggering, and nasal discharge. The onset of BRD should be expected after the weaning process, so producers should closely monitor every calf twice daily for the first few weeks after the weaning process. The onset of BRD can be rapid but most often appears with early clinical signs. Left untreated, calves with severe BRD will die from asphyxiation.
What are Treatment Options for BRD?
Early recognition and treatment of calves with BRD usually improves their outcome and overall performance. Treatment options can vary but most involve the use of antibiotics specifically designed to treat calves with pneumonia. Most producers now use antibiotics which are effective against the bacteria most commonly found in the lung tissue. These new antibiotics are also long acting, can be given under the skin (SQ), and very effective against BRD. In addition, some producers and veterinarians will also administer anti-inflammatory drugs for fever or vitamins. Response to therapy is usually observed within 24 hours and a successful outcome is closely related to early recognition of BRD clinical signs.
Diagnosis of BRD is usually made by clinical signs and response to treatment. However, necropsy is recommended on all dead calves to confirm the diagnosis of BRD and to find out which viruses and bacteria are involved. Necropsy can also provide answers on the nutritional status of the calf and which antibiotics may be most appropriate for treatment.
What are Prevention Strategies to Reduce BRD?
Prevention of BRD requires advanced planning and careful attention to herd health management. Decreasing the risks of BRD include good nutrition before weaning, reducing stresses related to handling and shipping, purchasing source-verified cattle from herds with a known health history, and vaccinating calves pre-weaning followed by booster vaccinations at weaning. Castrating and weaning calves while giving them time to acclimate to eating from a bunk prior to shipment is also a good idea. At processing, all calves should be properly vaccinated for BRD, ear tagged, implanted, weighed, and dewormed. In addition, any calves that appear sick or febrile should be treated with antibiotics during processing.
Mass medication (metaphylaxis) with long acting antibiotics given to all calves, on arrival, is another prevention strategy that has become more common. Extensive research has indicated that the number of BRD cases in treated calves, on arrival, is greatly reduced. In addition, treated calves will have improved average daily gain, feed efficiency, and overall performance. These factors support the use of metaphylaxis and have proven to be cost effective.