Ratty rat

Roban is a popular brand of rat poison to use and the farm I'm working on will buy 10kg tubs. Apparantly there are an estimated 2 million rats born every day in the UK. Some shops stock small packets to put down but they look mighty expensive compared to buying a tub and not sure how good the poison is. Don't like using it but seems like vermin control has to be done as well as owning a few hunting cats. Some people hunt them for sport with air rifles and terriers etc which sounds like a good idea.