Tess, I work in Public Health as a Health Laboratory Scientist at my states public health lab, so I am very aware of egggs and handeling reptile risks, and am as my wife calls me a "germophobic", but I am honestly more concerned about my boxies getting eaten by a dog or racoon, or myself getting in a car accident or murdered by a human, than salmonella or any other bacteria or virus. However your point is well taken and powdered calcium and gelatin are certainly a safer and readily available alternatives. I usually try to use natural food sources as I believe there may be other trace or intangible or unbeknownst to science, nutritional benefits.
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Jeff Benfer
gartersnakemorph.com