Magnesium oxide and magnesium sulfate contain more readily available magnesium than magnesite or dolomite limestone. Look at the bottom of the mineral tag under the ingredients heading to determine the source of magnesium in a particular mineral. Low consumption means low protection. Many producers report poor consumption of high magnesium minerals. This is why it is advisable to start cows on high magnesium minerals six to eight weeks prior to periods of critical need.
Some producers elect to leave high magnesium minerals with cows all year.
Never give cows a choice between high magnesium mineral and other minerals. Monitor consumption of the mineral. If cattle are not consuming the mineral, it does no good. If consumption is below desired level, consider moving the mineral feeder to a better location or adding concentrate to improve palatability. Agricultural Extension Service agents have ration formulations for preparing high magnesium supplements.