Mechanical factors influencing motility of rumen
When animal feeds, heavier boli they pass from oesophagus to cranial sac of rumen and are immediately passed into reticulum and omasum through reticulo-omasal opening. Heavier feed are retained less time for microbial fermentation.
Coarse particles of hay are retained for more hours than finely chopped hay. Fermentative activity and contractions of the pillars of rumen and reticulum result in physical breakdown of particles. Lighter particles (hay/straw) leave the cardia of the oesophagus to the dorsal sac of the rumen. They remain there for several days get soaked in the ruminal fluid for microbial action (rumen bacteria, protozoa and fungi).
Mixing and powerful crushing activity of contractions of the pillars help in through microbial digestion. This results in further breakdown because of microbial action and physical breakdown of particles during contraction of pillars and walls of the rumen and reticulum. This results in reduction of hay particles. Due to this the density increases and they settle down in the ventral sac. During contraction, the ingesta is pushed from ventral sac to cranial sac through cranial pillar of the rumen. From cranial sac via reticulo-omasal opening they are pushed into omasum and subsequently into abomasum.
Omasal transfer of substances
Ingesta from reticulum to abomasum is transferred via omasum. Omasum removes water and electrolyte from ingesta and reduces the size of the ingesta. Omasal canal act as pump and forces the ingesta into abomasum due to omasal contraction.
Contractile activity of the reticulo- omasal and omaso abomasal opening, walls of reticulum, omasal body and abomasum create the pressure gradient which aids in the flow of ingesta. Increase in reticular pressure dilates reticulo-omasal opening to push the ingesta into abomasum. Abomasum does not show rhythmic contraction similar to other three.