It seems that one of the objections to the use of ionophores, as well as conventional antibiotics, is the discovery of residuals in animal waste. It is claimed that since ionophores are not absorbed, but remain in the digestive tract until excreted, they then enter groundwater, and subsequently show up in the human water supply.

Recently, researchers from the University of Colorado found concentrations of ionophors in the sediment of the Colorado River bed. "While low concentrations are not necessarily a problem, we just don't know enough to say, 'Oh, these are low concentrations. Let's not worry about that,'" said Margaret Mellon, senior scientist at the Union of Concerned Scientists. The entire MSNBC article can be accessed here.

In a somewhat related (though 4 year old) study, researchers at Cornell University theorized that the use of ionophors with cattle has significant environmental benefits. As ionophores improved feed conversion, it reduced manure production. This, in turn, reduced the release of excess nitrogen into the environment as it leaches out of cow manure into ground and surface water.

The study also determined that methane and other greenhouse gas emissions were reduced by 25%. That study can be accessed in the Journal of Environmental Quality, here.

-z