Could be okay if that tenant leases that land and provided the pastureland has an agricultural exemption to keep taxes down. Ag leases should be separate from the lease the tenant has for the home or rental and outlines the responsibility for utilities, fencing, animal care and stocking rates on the farmland. There are lots of threads on controlling dogs and cats on this forum using park rules, and details on breeds, service dogs, etc.
If there is not an ag component here and no fencing then that tenant simply needs to get rid of those animals or leave the premises in accordance with your state laws. This is more likely what will happen in your situation.