Cows grazing on kosher-for-Passover feed in Ma'aleh Hahamisha, outside of Jerusalem.(Daniella Cheslow)

For those who adhere strictly to the laws of Passover, this is a busy time of year. Homes are purged of anything leavened, or anything that might become leavened. Out go the cereal, the crackers, and the flour. Just how strict we need to be when it comes to the presence of grain elsewhere in the food chain is a matter of some debate. In Israel, kosher certifiers insist that that for milk, eggs, and meat to be considered fit for the holiday, the cows and chickens from which they are derived must also be grain-free. Reporter Daniel Estrin went on a tour of a dairy farm outside Jerusalem to find just what this entails. [Running time: 6:20.]