Just want to add that when thinking about adding a supplement, always ask your vet first. They will know if it is necessary or if something else might be. When feeding high amounts of alfalfa, beet pulp, and also a jr feed or a high protein feed-please ask your vet if a phosphorous supplement might be needed. There are also health risks if the calcium to phosphorous ratio gets too high, not just the other way around.I do want to add that one must be very careful adding a vitamin/mineral supplement to a commercial feed when feeding young, growing horses. It's easy to really throw off the vitamin/mineral balance which greatly affects bones and joints.