Has anyone ever done a landlords waiver for livestock that grazes on leased property?

I don't understand your question and I have leased pasture of my own and ran cows on leased land. Can you be more specific?

Sounds like the TX statute for a lien on pastured livestock. See below. If you want a subordination or waiver of the lien from the landlord, then that's a legal document that your lawyer or loan platform vendor should be able provide.

From a practical standpoint consider this. If the cattle are on leased pasture and the loan defaults and you take possession of the cattle, wouldn't it be worth the "price" of cooperation to have the landlord protected for his charges? It would seem to me to be a negligible expense that assures some protection for your collateral until you can get the cattle moved.

Sec. 70.003. STABLE KEEPER'S, GARAGEMAN'S, PASTURER'S, AND COTTON GINNER'S LIEN'S. . . .(b) An owner or lessee of a pasture with whom an animal is left for grazing has a lien on the animal for the amount of charges for the grazing.