During a recent presentation, Jason Nickell, a researcher with KansasStateUniversity, discussed the importance of body temperature in diagnosing sickness in stocker cattle. “Body temperature is a direct reflection of the animal’s ability to balance heat gain and heat loss,” Nickell says. “However, a high rectal temperature alone typically cannot discern between conditions resulting in elevated temperature.” As a result, Nickell stresses that producers and consulting veterinarians need to interpret rectal temperatures in conjunction with other clinical signs in order to effectively determine a diagnosis and course of treatment.

According to Nickell, normal body temperatures for stocker cattle typically range from 100.5° F to 102.5° F. However, even healthy cattle can have body temperatures as high as 103° F during the summer months. Hyperthermia can result in cattle due to excessive heat production or a lack of heat loss. The latter situation is one that stocker operators need to be especially aware of when cattle are grazing fescue pastures. Fescue harbors a fungus that inhibits the ability of the skin vessels to dilate. For this reason, Nickell says that shade is especially important in fescue pastures.

Fever is similar to hyperthermia in that it is an elevation of core body temperature above that normally maintained by the animal. The rise in temperature is due to an inflammation or infection, not environmental temperatures. Fever is essential to fighting infection, but it can lead to animals going off feed and subsequent reductions in performance.

Nickell stresses that an elevation in body temperature is not the most accurate means of identifying if a disease condition is present, as there can be both environmental as well as animal-health reasons for the increase.  Nickell recommends that if a disease has progressed to the point that the calf displays clinical signs, then a rectal temperature should be obtained. Interpretation of the rectal temperature depends on many factors, including time of day, how much energy the animal exerted in being moved to working facilities, and what point in the disease process the calf is when examined. Nickell says that the last point is important, as a one-time body temperature reading is just a “snapshot” of the animal’s temperature at a given time.

“A calf pulled for a first-time episode of BRD may likely possess a rectal temperature of 104° F or greater,” Nickell says. “On the other hand, a calf with chronic BRD may display many of the same clinical signs as the first calf but possess a normal rectal temperature.” The two calves are at different stages of the disease process.

As part of his presentation, Nickell also says that the instinctive nature of cattle, as animals of prey, to suppress any evidence of sickness or debilitation from a threat, such as a human, can also prevent timely identification of illness based on clinical signs alone. An experimental eartag device was used in a KansasStateUniversity study, and the data demonstrate that calves’ body temperatures typically were elevated two to three days prior to actually being pulled for BRD based on clinical signs.

The calves still responded well to treatment, but determining if an elevated body temperature exists prior to the exhibition of clinical signs might allow for more prompt treatment and would allow calves to return to normal feed intake within a shorter amount of time.