In this answer to another question, someone mentioned that they got gelatin out of rendering cow fat. I'm about to render a bunch of cow fat in a few days, and I was wondering how to get gelatin from it, in addition to the tallow? (i.e. I don't want to accidentally throw any good non-tallow parts away)  Do I have to use 'suet' or can I use any cow fat? I'm just getting "the fat" from a cow, and it's probably going to be mixed together. 
When I render fat scraps (usually taken from brisket and shoulder roast), there is usually a significant amount of connective tissue mixed in (although I try to trim away all of the meat). Thus, after rendering the tallow and letting it cool, the liquid below the tallow is quite gelatinous. It is a whitish color. It is thicker than a typical stock, although not quite as thick as calf's foot jelly. I save this and use it to thicken broths and soups (although it doesn't have much flavor, so I don't use it by itself). 