Jamieson, Fausset and Brown on Ezekiel 34:3

3. fat--or, by differently pointing the Hebrew, "milk" [Septuagint]. Thus the repetition "fat" and "fed" is avoided: also the eating of "fat" would not probably be put before the "killing" of the sheep. The eating of sheep's or goats' milk as food (De 32:14; Pr 27:27) was unobjectionable, had not these shepherds milked them too often, and that without duly "feeding" them [Bochart], (Is 56:11). The rulers levied exorbitant tributes.

kill ... fed--kill the rich by false accusation so as to get possession of their property.

feed not ... flock--take no care of the people (Joh 10:12).