Abstract: Feed supplements for ruminant animals particularly buffer blocks for dairy cattle. The buffer block is prepared by forming a mixture containing at least about 60% by weight of buffer materials other than magnesium oxide (preferably sodium bicarbonate and/or sodium sesquicarbonate), at least about 20% by weight of magnesium oxide, and no more than about 16% by weight of a sugar-containing binder (e.g. molasses), and then shaping and compressing the mixture at a pressure of at least about 2800 pounds per square inch (19,306 kPa) for at least 8 seconds. The resulting block is acceptable to the animals despite its large content of buffer ingredients and has suitable physical and chemical properties for use as a free choice feed supplement block despite the simple and economical preparation process.