It used to be that a lot more of the animals we hunted and harvested, or raised and slaughtered, were used or consumed directly by us humans. Gradually, we've discovered that some parts are not as useful/good for us as we used to believe.

For the most part, organ meats, while providing a variety to normal muscle tissue consumption, also had some additional nutrient value thought to be worth the trouble of processing them. Liver provides a good source of vitamin A, and organs tended to have higher mineral content and other vital nutrients. Unfortunately, organs also tend to have more disease related issues with their consumption. Anymore, eating any part of the central nervous system is discouraged due to BSE and CWD, which bioaccumulates and can cross contaminate. E-Coli also became a lot more prevalent, thus dissuading the consumption of any part of the digestive system. As well, synthetic replacements became readily available on the market that were cheaper to produce, much safer, and generally more functional (sausage casings and such).

Consequently, a goodly portion of the animals we process commercially go to pet food, fertilizer or other indirect consumption, like hides into leather. Having worked in an "Iowa Beef" processing plant, I got to see firsthand what went where, and learned pretty quick that standing up to your chest in a pit full of cow guts while unjamming an auger isn't going to kill you, and doesn't have to make you nauseated. If you choose to let it bother you, then it will, but you can control that if you want. I was told that the first time I killed a deer and had to dress it I would get sick, but it never happened, and I have to say it is because I made up my mind that it wasn't going to bother me. It's not like motion sickness, where you have to deal with real physical effects. Unless you have some unusual biological trait like an allergic reaction, the smells, sounds, and touch of processing dead animals has no effect on a person except psychological, so long as you take proper hygenic precautions.

Because I have pets and usually process the hide of the animals I harvest from the wild (not so much birds, but certainly deer sized game and bigger), I'd say I utilize about 90% of what I take. Some of the bones I render for stock, and some go directly to the dogs. For birds I'd say maybe 75 to 80% because I don't have much use for bird feathers. For fish, it is at least 90%, about half the time I will use the heads to make fish stock with.

Pigs are perhaps less wasteful than most, if you are willing to use the organ meat. I grew up eating cured pork meat with the rind still on, and I have teeth capable of masticating the rind (cured skin) fairly efficiently, and I've eaten pig's feet and ears, though I would prefer making a treat of those for my dogs nowadays. The only trouble with pigskin was when grandma wouldn't get all the hair off and you'd have to pick it out of the mouthful you'd be chewing on. Hog casing is the most commonly used natural sausage casing.

If you really think you are going to have a problem with getting ill while field dressing game, then I suggest going without food for a couple days then attend a hog butchering and take some of the meat and cook it up with a little creole seasoning and eat it directly. Your stomach will convince your brain that what you saw is no big deal when that meat comes off the bbq and you get a whiff and a taste of it, I gar-on-tee! After that, I bet you won't get so squeamish no more.