Time to read feed labels! I've been looking at the label on my current brand of rabbit feed and it contains an ingredient called D-activated animal sterol (a source of vitamin D). The "animal" part caught my eye, since I'm not sure if herbivores should be eating animal protein, so I decided to see what I could find out about it. Apparently the "animal sterol" part is a substance found in fat and skin and "D-activated" means the animal sterol was treated with ultraviolet irradiation to form vitamin D. So basically scientists created a sustance in the laboratory that duplicates the end product of what happens when people or animals go outside on a sunny day and their skin synthesizes vitamin D from exposure to sunlight. (http://www.beyonddiscovery.org/content/view.page.asp?I=434 has a fairly indepth article describing the discovery of the mechanism behind vitamin D in relation to human rickets.) So what's worse: sythetic chemical vitamins or more "natural" supplements formed from animal protein? Does anyone know more about this and does an animal that gets adequate exposure to sunlight even need this supplement? Any thoughts would be appreciated.