Hi all,
For once, I actually have some knowledge on this topic. I'm a graduate student and am doing some research on silver in the environment - about how to detect and understand what form silver might be in the environment - but anyway...
I can't understand the popularity of colloidal silver. Yes, it certainly has anitmicrobial properties. But it's also extremely toxic to humans and other animals. You can find its toxicological data here:
http://toxnet.nlm.nih.gov/cgi-bin/sis/search/f?./temp/~R49Pnx:3
Silver is more toxic in the dissolved form than in the nanoparticulate (colloidal) form. One commercially available product I've done testing on actually contains some dissolved silver as well as colloidal silver. Another worry about people taking colloidal silver is that larger particles may accumulate in the body and act as a source of dissolved silver.
As for chickens, they are much smaller than us, so the amount of silver needed to cause argyria or a toxic response is much less than what we would need. Although species can really vary in their toxic responses, a general rule of thumb is that toxicities are measured in mg dose per kg of body weight. So if a chicken weighs 5 pounds, or 1 thirtieth of a 150 lb adult, for whom doses are typically calculated for, then you should only give a chicken a thirtieth of the dose called for, if you are going to try this.
It's certainly true that people are not keeling over and dying because of colloidal silver. But, my guess is that long term chronic exposure could do real harm to organs, though I haven't done the research to back this up. But in my mind it makes sense that the body is harmed by a metal it doesn't normally have to deal with.
We also spent a lot of effort time and money trying to get chemical, mineral, and photo companies, like Kodak, to clean up their act and prevent and treat silver releases to the environment. Now maybe thousands or millions of ordinary consumers are buying 10 ppm colloidal silver suspensions, and all of that silver goes somewhere ... your wastewater treatment plant is not designed to remove silver from wastewater, so much of it is released to the environment.
I'll get off my soapbox now.
-Emily