Management practices may actually contribute to cattle’s “ill health.”
By Mark Spire, D.V.M.
Intervet/Schering-Plough Animal Health
Cattle, like other mammals and humans, have developed a complex adaptive response to a variety of diseases or illnesses. This response is called “sickness behavior.” Sickness behavior is highly evolved in animals to combat viral, rickettsial, protozoal and bacterial infections and related toxins. When animals were in their wild state, it was absolutely necessary for their survival. Does the same apply to today’s typical sick calf? You bet!
Animals responding to severe local or systemic inflammation will have a fever, muscle weakness, lethargy, malaise generally expressed by reluctance to move around or associate with herd mates, will groom less, will lie down more (saves energy and increases sleep) and will go off feed and drink less. These behaviors offset more metabolically expensive behaviors such as grazing or walking to water and decrease energy loss while increasing heat production.
Cytokines are the culprit
What is a major contributor to sickness behavior? Cytokines! Cytokines are any number of substances secreted by virtually all nucleated cells in the body.
During an infection like pneumonia, immune cells recognize a pathogen and become activated. In the case of gram negative pathogens, endotoxin produced by the organism is what is recognized and activates the immune cells. Cytokines act to facilitate intercellular communication by regulating the animal’s responses to infection, further activation of the immune system, inflammation and injury.
Some cytokines can be anti-inflammatory while others, particularly those that induce sickness behavior, are pro-inflammatory. Anti-inflammatory cytokines work to keep the reactivity of pro-inflammatory cytokines in check, thus preventing extensive tissue damage.
While necessary to overcome an infection or resolve an injury, this cascade of pro-inflammatory responses comes at a metabolic cost to the animal. The immune system response requires vast amounts of energy for tissue repair, increased metabolism and for fever maintenance.
Yet, fever alters eating and drinking behavior. Cattle with pneumonia spend less time eating and drinking and have reduced feed efficiency. This phenomenon is occurring at the same time that the animal’s response to a febrile condition is increasing protein and energy metabolism. This is especially critical in newly arrived or weaned cattle as they are already in a negative protein and energy balance due to transitional changes in the rumen following transportation and dietary changes.
Management practices could be a contributing factor
A basic contributor to why cattle may be showing “sickness behavior,” yet not actually having pneumonia at this point in time, is the unintended consequences of the management procedures used in the operation. A number of injectable products commonly used in cattle are pro-inflammatory. These include, but are not limited to, clostridials, oil-based vaccines, certain other adjuvated products, vitamin/mineral products, antibiotics particularly those containing glycerol formal or propylene glycol, bacterins and avermectins.
While acting singularly, these products may not contribute to the amount of inflammation that could cause a cascade of the inflammatory response. The use of multiple pro-inflammatory products coupled with the use of products potentially containing endotoxins such as Salmonella, Mannheimia, Pasteurella, E. coli, Histophilus, Morexella, Brucella, Campylobacter, Leptospira and Fusobacteria vaccines could induce “sickness behavior” as small amounts of endotoxins cause dramatic behavioral and immunological changes.
We are asking much of newly arrived cattle. We routinely train cattle health care providers to let the cattle tell us when something is wrong with them. We do it by close observation of clinical signs the cattle may be presenting. We are rapidly discovering that cattle display “sickness behaviors” that may indicate that they are ill, but we can not assume that it is BRD and be arbitrarily treating or revaccinating. Our management practices may actually be a contributor to their “ill-health.”
For more information about sickness behavior in dairy animals, contact your veterinarian or animal health provider.
Dr. Mark Spire is a technical services veterinarian for Intervet/Schering-Plough Animal Health. He lives in Kansas and can be contacted at 785-537-3857 or firstname.lastname@example.org.