Why do laws take so long to be enacted?

The Michigan legislature recently sent a bill to the Governor regarding improved standards for farm animal care in the state. However, the changes for calves take 3 years to take effect, and the changes for pigs and chickens take TEN YEARS to be enforceable! I understand that facilities that deal in these animals need time to adjust to the new standards, but why 3 and 10? Seems a little much to me. Is there something I'm not seeing? Thanks all!