I thought I remembered that corn cob bedding was not a good choice, but couldn't remember why, so I googled it to see. I found this, which is definitely not what I remembered, but it was very interesting:
http://www.pubmedcentral.nih.gov/art...?artid=1314908
The summary is that corn cob bedding has been shown to block male and female sexual behavior and disrupt the female's estrous cycle in rats. So I guess not a good choice for breeding feeders!
I also found another page that discussed this and said that the chemical that causes this effect has been found in fresh corn and in corn products such as corn tortillas. The point was that it is definitely in the corn...not a contaminant. But it makes me wonder about all the rodent feeds that use a lot of corn. It is the major ingredient in Mazuri 6F, for example. Hmm.