In a major study by Cornell University in 2018, researchers found that water troughs on farms are a conduit for the spread of toxic E. Coli in cattle; which can then spread this pathogen to people through this toxic bacteria in feces-contaminated beef and salad greens.
"As it does not make the cow sick, farmers do not see a problem" summarizes Renata Ivanek, associate professor of epidemiology in the College of Veterinary Medicine and the paper's senior author.
The researchers ran mathematical modeling studies to see if they could pinpoint areas in the farm where infections might spread between cattle. They found that water in a trough, especially in summer months, could heat and promote pathogen replication, causing more cows to acquire the bacteria when they drink.
Part of their research was running control trials in a feedlot over two summers. The researchers were surprised to learn that the typical water trough found on farms, (which automatically refill when they get low enough, and can be adjusted to refill more often thus saving water and keeping it fresher,) actually found an increase of the toxic E. coli (0157:H7). In fact, they found it to be about 30 percent higher than the control pens where the troughs had more water.
Further research is planned but the gist of this article is:
Clean and sanitize your water troughs regularly
Keep them refreshed with cool water
Keep them full. The more water the better!
Also, see the post "Livestock Water - From Green to Clean"
You can read more about this study and come to your own conclusions at http://www.news.cornell.edu by Krishna Ramanujan, February 26, 2018.