Vigilance in Monitoring Calf Health Following Exposure to Wildfire Smoke

After exposure to wildfire smoke, vigilance will help calves stay healthy. Photo by Chabella Guzman

By Brock Ortner, UNL Extension Educator

Wildfires occurring in western and central Nebraska mirror a broader trend of

increasing wildfire frequency and magnitude across the western United States. While

the immediate impacts of wildfire are devastating to beef production and rural

communities, the effects of wildfire smoke may also pose risks to both human and

animal health. In the weeks and months following a wildfire event, producers should

remain vigilant and monitor calves for signs of respiratory disease or illness.

Combustion of biomass during wildfires produces carbon dioxide and water vapor but

also generates ash, a mixture of inorganic compounds. Of particular concern is

ultrafine particulate matter (< 2.5 µm), which can travel deep into the lung alveoli

and enter the bloodstream. In humans, these particles have been associated with

inflammation and oxidative stress.

Limited research has examined wildfire smoke exposure in cattle. However, work

conducted by Ranches and others (2026) in a small group of Simmental × Jersey calves

reported increased concentrations of cortisol, an indicator of stress, following

exposure to smoke from a wildfire approximately 10 miles away from the study site.

In the same study, concentrations of ceruloplasmin, a marker of systemic

inflammation, were elevated following the wildfire event. Antibodies including IgM

and IgA were also increased, suggesting activation of the immune system.

Physiological stress and inflammation can negatively affect cattle performance and

immune function. When immune defenses are compromised, calves may become more

susceptible to respiratory pathogens. In the development of bovine respiratory

disease (BRD), opportunistic bacterial pathogens-including Mannheimia haemolytica,

Pasteurella multocida, Histophilus somni, and Mycoplasma bovis-are normally present

at low levels in healthy calves. However, when viral infection or physiological

stress suppresses immune function, these bacteria can proliferate in the respiratory

tract, leading to morbidity, reduced performance, and potentially death.

Because stressors such as wildfire smoke may increase disease susceptibility,

monitoring calves closely for early signs of illness is important. One practical

approach is the D.A.R.T. method, which helps producers identify calves that may

require further evaluation.

D - Depression:

Observe calf posture and behavior. Droopy ears or head carriage, lethargy, increased

time spent lying down, and separation from pasture mates may indicate illness.

Because cattle are prey animals and tend to hide sickness, subtle behavioral

differences may only become apparent after calves become accustomed to your

presence.

A - Appetite:

Reduced appetite-whether at the feed bunk or during nursing-can indicate a health

challenge. On pasture, reduced gut fill relative to herdmates may also signal

decreased intake.

R - Respiration:

Healthy cattle typically take 10-30 breaths per minute. Increased respiratory rate,

shallow breathing, or abnormal sounds such as coughing or raspy breathing may

indicate respiratory disease. Nasal discharge or excessive eye secretions may also

accompany illness.

T - Temperature:

Rectal temperatures of approximately 103.5-104.0°F or greater are indicative of

fever and warrant further attention.

Early detection and treatment of sick calves improves the likelihood of recovery and

helps reduce performance losses associated with respiratory disease. Extra vigilance

and responsiveness may help mitigate adverse health outcomes in the weeks and months

following exposure to wildfire smoke.