Reference for Chullin 205:28

בהמה בחייה לאברים אינה עומדת איסור אבר ואיסור טרפה בהדי הדדי קאתו

Alternatively, you may say, all agree that an animal whilst alive does not stand to be dismembered into limbs, but they differ whether or no the prohibition of the limb [from a living creature] can be superimposed upon the [existing] prohibitions of the forbidden fat and of trefah.

Jastrow