no, if the grass is good, you should be fine without hay during the late spring and summer. Just make sure they have good water. You should probably also put out minerals and salt. We also like to feed range cubes a few times a week, especially in the colder months when our cows are pregnant. In the winter we put out the hay, usually two round bails at a time per 15 head, and let them eat the bails about 95% down, then put out some more. How many bails you put out really depends on how often you want to feed. We like to make sure they always have hay during the winter. Others may do things a differently, but I hope this helps.