Bovine respiratory disease (BRD) has long been an issue plaguing cattle producers. BRD is the deadliest and costliest disease that producers contend with, accounting for 37 percent of the mortality on cow/calf operations and 57 percent in feedlots.
BRD is caused by a host of viral and bacterial pathogens which, when combined with environmental, nutritional or physical stressors that suppress the immune system, make BRD difficult to treat. To defend animals from the disease, producers should consider not only what pathogens to vaccinate against, but also the management practices they can implement to reduce stress, and the options available should treatment be necessary.
How Stress Affects BRD
Stress is directly related to an animal’s ability to fight off an infection. Stress has been shown to cause a release of hormones, including cortisol, which can have a negative impact on the immune system and make the animal more susceptible to disease. Further, stress can be additive, suppressing the immune system more. Cattle that are exposed to pathogens that can cause BRD, such as Mannheimia haemolytica, during these stressful periods are more likely to become infected.
A wide range of events can cause stress on an animal. Nutritional factors include dehydration, nutritional deficiencies or abrupt changes in feed, while environmental elements, such as weather changes, dust or dampness, and exposure to fumes and respiratory irritants also can contribute negatively. Events that affect the animal physically might be the most prevalent risk factors for BRD, including weaning, castration, processing, shipping and commingling.
With such a wide range of factors at play, producers should examine their management practices to determine where stressors are present and how they can mitigate them.
Managing Stress to Manage BRD
Managing an animal through a stressful period could have real impact on the number and severity of animals getting sick. Reducing this stress, and therefore disease, translates to better weight gain and production and lower health cost and death losses. This results in economic benefits for the producer, making managing stress worth the extra time and effort.
To help reduce stress on animals, producers can consider avoiding processing, weaning or shipping cattle in bad weather when possible. Making sure the animal has sufficient water and feed access, including acclimating calves to water troughs and feed bunks, can also contribute to reducing stress. Research has shown that feed intake is important as a preventative measure in regard to BRD, especially during weaning when calves could stop eating and drinking due to the stress of the change.5 Offering feed and forage before weaning can help soften the impact of the change, and some producers have seen success with using older “trainer” animals to help show weaning calves or new arrivals at an operation where and how to use feed bunks and waterers.
For some producers, fence-line weaning can offer a lower-stress environment for cows and calves, with calves showing less incidence of disease and higher weight gain in fence-line weaning programs over abrupt weaning. When possible, producers should also separate shipping and processing from weaning. While it might not be as easily managed on some operations, some value-added programs now require calves be weaned at least 45 days before shipping. This allows the calf to recover from the stress of weaning and can drastically reduce the incidence of BRD. Castration, branding, ear tagging and vaccinating can also be done at least three weeks prior to weaning to help reduce the impact of stress on calves. Vaccines are likely to be less effective while the animal is under other stressors such as weaning, so separating these processes can help the animal develop a better protection against the pathogens that can cause or contribute to BRD.
Preconditioning an animal before shipping, or allowing it to adjust from other stressors like weaning, can have significant effects. One study showed up to a 16% decrease in feedlot morbidity related to respiratory disease in calves that had been properly preconditioned, while another study showed that preconditioned calved were two times less likely to develop respiratory disease and five times less likely to require treatment.
When Stress Can’t Be Avoided
While limiting stress on calves is an ever-present need, stress that calves experience can never be eliminated. Calves must be weaned, cattle have to be shipped and weather can’t be controlled. When the risk factors for BRD can’t be mitigated, producers need additional help to maintain the health of their herds. Immunostimulant products that are applied at the time of a stressful event can help an animal jumpstart its immune system before it is faced with pathogens associated with BRD.
Immunostimulants broadly and effectively stimulate the innate immune system, which is the first line of defense against pathogens. This compares to antibiotics, which target one or several pathogens to fight infection directly, or to vaccines, which contain specific antigens and typically/primarily trigger a specific adaptive immunity response to the antigens contained in the vaccine. Immunostimulants help the animal’s own body fight off infections, particularly at times when the immune system might otherwise be suppressed due to outside stressors. An immunostimulant such as Zelnate® DNA Immunostimulant has shown to reduce mortality associated with BRD due to Mannheimia haemolytica, so this may represent an important additional technology to consider for helping to limit BRD losses.
Producers may not be able to completely take stress out of the lives of their animals, nor can they completely eliminate BRD. However, through using low-stress management practices when possible and additional tools like immunostimulants, producers can reduce the impact that BRD can have on their operations.