This is a highly hypothetical question because of a book I'm trying to write.. If a world was to be populated with animals for farming purposes and left mostly alone for 50 years between harvesting the stock would the planet also need to have predators as well? To be clear the animals need about 50 years to mature enough for the first generation to be grown to full size. If there were no predators and these were all plant/grass feeders, what is the minimum number of"helper" species would you need to introduce ie: pollinators? Thank you in advance for your time and consideration. Cathy