You don't need to see a cattle yard to identify its existence; the smell alone is usually enough. Now, though, you're breathing in not just the aromatic compounds you likely know well — but a selection of antibiotics and antibiotic-resistant DNA too.
A new study by researchers from Texas Tech University sought to explore the airborne transmission of antibiotics from cattle yards. During a six-month period, the team gathered air samples — both up- and down-wind — from 10 commercial cattle yards within 320km of Lubbock, Texas. Each of the yards was home to between 20,000 and 50,000 cattle.
Analysis of the samples revealed that the sample taken down-wind were dramatically different to those taken up-wind, containing a wide range of particulate matter. In particular, the researchers found the antibiotics tetracycline, chlortetracycline and oxytetracycline in 60 per cent the downwind samples. Oxytetracycline was found in all of them.
"[Particulate matter] generated at beef cattle feedyards contains distinct communities of bacteria, antibiotics, and antibiotic resistance gene sequences," write the authors. "Thus there is significant potential for widespread distribution of antibiotics, bacteria, and genetic material that encodes antibiotic resistance via airborne [partoculate matter] as a result of the large mass of fine particles released daily from beef cattle feedyards in the Central Plains of the United States."
The researchers also point out that distribution can be further fuelled by "significant wind energy potentials and frequent wind events in this region." Given that the consumption of antibiotics and antibiotic-resistant DNA by humans can lead to antibiotic resistance, this mode of transportation is of some concern — especially for the vegetarians among us. [Environmental Health Perspectives via Raw Story]