This year, I chose to do the digestive system. The board I made had pipes running to each section of the system. When it came time for my presentation, I put colored water into the pipe so I could show the "food" traveling through out the system.
The digestive system of cows is much different from pigs or horses, because cows do not have acid in their stomachs to digest food. Instead, the food takes a round about path through different parts of the stomach for rumination, back up to the mouth (as a cud) for further chewing, and then back again so that the grass or grain can be broken down enough for nutrients to be available when the food travels to the intestines.
When cows and other ruminants are fed grain, as George is, it is very important to make sure they also get plenty of roughage, like grass or hay, to prevent too much gas from building up in their stomachs and causing diarrhea or bloat.
While I was preparing my presentation, I got to get some hands-on expertise with my topic. George and our bull Norman both had some mild bloating. It was not severe, but because bloat can kill an animal if it's not treated, we had to act fast. Fortunately, their case was mild enough that we were able to ease their symptoms by just walking them around for a few hours and giving them plenty of hay. My dad was pretty nervous. (We have a LOT of money invested in those two animals!) Once we heard George and Norman passing the gas as they walked, I am sure my dad felt as relieved as they must have felt!