Function of the bovine omasum in ingesta transfer

Abstract

Motor events in the omasum were studied by recording reticulo-omasal pressure changes and attempting to correlate these with ingesta flow. Fluid-filled, open-tipped catheters and strain gauges were used. Ingesta flow was studied by fluoroscopic examination, palpation, a funnel-reservoir system and by use of the Pitot tube principle. Results indicated that the omasal canal undergoes contraction with each primary and secondary contraction of the rumen. It is proposed that omasal canal contractions force more fluid components of the ingesta from the canal between the leaves of the omasal body. Canal contractions were often followed by contraction of the omasal body which forced accumulated fluid ingesta into the abomasum. The greatest flow of ingesta from the reticulum appeared to occur directly following the canal contractions. Backflow of large volumes of ingesta from omasum to reticulum was occasionally noted and seemed to occur when the omasal body contracted during closure of the omaso-abomasal orifice. Implications of this are discussed.