THE reason you should keep new stock separate is to try and stop any transfer of parasites/disease . Ideally new sheep should be wormed/ fluked scab prevention before leaving the sellers property , so allowing time to work while the sheep are traveling , then on arrival wormed again with a different wormer group, treated for lice/keds/ticks and kept on concrete or in a shed for 24 hrs , then any bedding burned . the sheep can then go out into a totally seperate field ( no contact at all even through a wire fence ) for at least 2 wks ideally 4wks , and remember your clothes boots can transfer as well . Sorry don't understand the land question ??