..dang that doesn't quite work (for those musical history theatre buffs out there)...

ok where is Rancher -> food = horses handled, I looked both in the stable and at the rancher and neither seem to handle the actual ratio of food/horse in the xml file. did I just miss it?

same with education btw, if anybody knows.

For horses, the answer is that all city dwellers consume as much yield as they produce (modulo production modifiers). It is a "hard coded" 1:1 ratio. The engine has no ability to represent a different ratio without modding the DLL.

Education code is special handled in the DLL, but I haven't read it :/. CvCity::doYields() would be the place to start for that, depending on what you want to do. There are learn rates for professions as well in the XML layer.

Yes you can easy change it in the xml file - Assets\XML\Buildings\CIV4BuildingInfos.xml

Native stable have a 100% production bonus. One guy working, taking 2 food to produce 4 horses per turn.

Edit: Correction. You get one free house production with native stable, so one man converts 2 food to 3 house with a 100% bonus giving 6 horses.

It's handled in the building infos, as already noted.