Abomasal disorders include left displaced abomasum (LDA), right displaced abomasum (RDA), abomasal volvulus (AV), abomasal ulceration, and impaction. Displacement or volvulus is seen most commonly in dairy cows but can also be seen in dairy bulls and calves. Except for AV, abomasal displacement is rare in beef cattle and essentially undiagnosed in small ruminants. Abomasal ulcers are seen in dairy and beef cattle and in calves and lambs; they are rarely diagnosed in small ruminants. Impactions can be primary, which is most frequent in beef cattle, or secondary, which develop most often in dairy cows as a form of vagal indigestion. Impactions may have a hereditary basis in some black-faced sheep.