Use baby Rex and Bronto bodies to feed to it, they will increase the trust bar the most. While riding on it to tame, you can bring more baby Rexs and Brontos to kill and eat since they increase the tame bar by a lot too. It will not eat meat in its inventory after you tamed it so you'll have to ride around and kill things and eat the corpses to actually feed it otherwise it'll die of hunger and all your hard work will be gone ☹️ great tame tho and well worth the risk. Hope this helps 👍