Effects of wildfire smoke exposure on innate immunity, metabolism, and milk production in lactating dairy cows

Abstract

Wildfires are particularly prevalent in the Western United States, home to more than 2 million dairy cows that produce more than 25% of the nation's milk. Wildfires emit fine particulate matter (PM 2.5 ) in smoke, which is a known air toxin and is thought to contribute to morbidity in humans by inducing inflammation. The physiological responses of dairy cows to wildfire PM 2.5 are unknown. Herein we assessed the immune, metabolic, and production responses of lactating Holstein cows to wildfire PM 2.5 inhalation. Cows (primiparous, n = 7; multiparous, n = 6) were monitored across the wildfire season from July to September 2020. Cows were housed in freestall pens and thus were exposed to ambient air quality. Air temperature, relative humidity, and PM 2.5 were obtained from a monitoring station 5.7 km from the farm. Animals were considered to be exposed to wildfire PM 2.5 if daily average PM 2.5 exceeded 35 µg/m 3 and wildfire and wind trajectory mapping showed that the PM 2.5 derived from active wildfires. Based on these conditions, cows were exposed to wildfire PM 2.5 for 7 consecutive days in mid-September. Milk yield was recorded daily and milk components analysis conducted before, during, and after exposure. Blood was taken from the jugular vein before, during, and after exposure and assayed for hematology, blood chemistry, and blood metabolites. Statistical analysis was conducted using mixed models including PM 2.5 , temperature-humidity index (THI), parity (primiparous or multiparous), and their interactions as fixed effects and cow as a random effect. Separate models included lags up to 7 d to identify delayed and persistent effects from wildfire PM 2.5 exposure. Exposure to elevated PM 2.5 from wildfire smoke resulted in lower milk yield during exposure and for 7 d after last exposure and higher blood CO 2 concentration, which persisted for 1 d following exposure. We observed a positive PM 2.5 by THI interaction for eosinophil and basophil count and a negative PM 2.5 by THI interaction for red blood cell count and hemoglobin concentration after a 3-d lag.Neutrophil count was also lower with a combination of higher THI and PM 2.5 . We found no discernable effect of PM 2.5 on haptoglobin concentration. Effects of PM 2.5 and THI on metabolism were contingent on day of exposure. On lag d 0, blood urea nitrogen (BUN) was reduced with higher combined THI and PM 2.5 , but on subsequent lag days, THI and PM 2.5 had a positive interaction on BUN. Conversely, THI and PM 2.5 had a positive interacting effect on nonesterified fatty acids (NEFA) on lag d 0 but subsequently caused a reduction in circulating NEFA concentration. Our results suggest that exposure to high wildfire-derived PM 2.5 , alone or in concert with elevated THI, alters systemic metabolism, milk production, and the innate immune system.

National dairy research programs: what is their role in animal health and sustainability research?

“…15 There is also increasing evidence that heat stress and other climatic changes have clinically relevant impacts on dairy cows and are likely to become greater issues in much of the US in the coming years. 16,17 Clearly, there are many questions about the impacts of animal health on environmental sustainability and there remains a sizable need for research to address these questions.…”

Camera traps link population-level activity patterns with wildfire smoke events for mammals in Eastern Washington State

“…Other health metrics provide a more nuanced picture of the effects of smoke in particular on large animal health. For example, a recent study directly linked exposure to PM 2.5 from wildfire smoke to negative health effects in dairy cows, including reduced milk production, altered metabolism, and changes in blood immune cell composition (Anderson et al 2022), and a study of captive rhesus macaque monkeys (Macaca mulatta) found that exposure to smoke as infants led to reduced lung volume as adolescents (Black et al 2017). Case studies from veterinary medicine indicate respiratory and neurological effects of smoke exposure for cats (Felis catus) and dogs (Canis familiaris) (Drobatz et al 1999a, b).…”

Wildfire smoke linked to vocal changes in wild Bornean orangutans

“…For example, farm animals exposed to smoke show low conception rates, poor weight gain, and decreased milk production. 15 Likewise, 2-to-3-month-old captive infant rhesus macaques ( Macaca mulatta ) exposed to 10 days of high particulate matter (PM 2.5 = particles measuring < 2.5 μm in diameter) concentrations from wildfire smoke showed reduced lung capacity and weakened immune responses at age three. 16 In that same colony of macaques, pregnant females who were exposed to 12 consecutive days of elevated PM 2.5 concentrations (i.e., exceeding 35 μg/m 3 ) experienced greater pregnancy loss compared to females who were pregnant during periods of healthy air.…”