Anatomy, Development, and Functions of the Bovine Omasum

Abstract

Summary Numbers of laminae and their arrangement varied significantly among omasums of different cattle and between the upper and lower portions of the omasums of 85 among 86 organs examined. Pedunculated shape of, and partial blockage by the first-order laminae at the reticulo-omasal orifice, and their extension generally across to the sulcus omasi, tend to allow mainly small feed particles to enter, and divert them between the laminae. From ingesta samples air-dried, some reduction in size of particles was found in the omasum to under 1mm in diameter. Digestion and solution of fine ingesta caused rapid removal of fine particles in the abomasum. Significant differences were found in numbers of laminae among animals and between upper and lower portions of the omasum (P Volume of the full omasum increased to 60 times between 10 and 150 days of age. Moisture contents of omasal contents decreased markedly from those of the rumen and reticulum, without respect to age in these calves.