What right does the landlord have about the removal of livestock on his property that do not belong to him but to the former people who used to live there?

The Landlord rents you space if you agree to follow the rules, if he/she says ''No Cows" and you bring a cow, they have the right to remove it

Another View: The question reads like the former tenants (who owned the livestock) are no longer tenants and left their animals. If that is the case it becomes a case of 'abandoned property." The landlord will have to comply with the laws concerning abandoned property that are in effect in his municipality or state.