It’s impossible to keep much sterile on a dairy, but could clean udder cloths be transmitting mastitis-causing bacteria in the milking parlor? A recent study of 67 U.S. dairies in ten states investigated whether there is an association between the bacteria levels in (clean) cloth towels and the health of the udders those towels were used on. The authors measured bacteria on clean towels and in milk samples. They also looked at towel use and laundering practices.

What did they discover?

• ~20% of udder quarters were infected
  • 10% non-aureus Staphylococcus species
  • 4% Staphylococcus aureus
  • 5% Streptococcus or Strep-like organisms
  • 4% other gram-positive bacteria
  • 2% gram-negative bacteria (includes coliforms)
• No towels were free of bacteria. The mean overall bacterial count was 3.77 log₁₀ cfu/cm² (cfu=colony forming units).
• Bacillus species were the most commonly found (95% of cloths). Approximately half the towels contained Staph and/or Strep species.
  
• Only Staphylococcus species and Streptococcus species counts on towels were associated with mammary infection rate.
• No towels laundered off-site by a service had high coliform counts. Also, undried towels had higher coliform counts.

Now, the study authors note that they have not demonstrated that new infections are necessarily being introduced from bacteria on clean towels, just that they found a positive association between Staph and Strep infections and the presence of those organisms on clean towels. However, given their findings, they suggest getting clean towels tested and then working to get those bacteria levels to essentially undetectable for Staph, Strep, and coliform species. Changes in laundering or storage practices could help. (When was the last time the clean towel bin was washed?)

The bottom line: Dry udder cloth towels after washing. Get clean towels tested periodically to see if they may be carrying mastitis-causing bacteria.

The paper:

Rowe et al. Cross-sectional study of the relationship between cloth udder towel management, towel bacteria counts, and intramammary infection in late-lactation dairy cows. Journal of Dairy Science, December 2019, 102:11401-11413. DOI: https://doi.org/10.3168/jds.2019-17075