There are two patterns of motility are seen in reticulo-rumen
Primary or mixing contractions called primary cycle
Secondary or eructation contractions known as secondary cycle
Primary contractions
The primary cycle consists of
a biphasic contraction of reticulum
a caudal moving single contraction of dorsal sac
a contraction of ventral sac of rumen.
In the primary cycle, rumino-reticular contractions begin from the reticulum as biphasic contractions of which the first contraction known as mixing contraction.
It then relaxes.
The second contraction with strong force is called as evacuation contraction.
During feeding, the contractions occur at 75 seconds intervals.
Functions of reticular contractions
Direct liquid flow caudally to the cranial ruminal sac
Direct low density ingesta into the dorsal sac
Assist in regurgitation
Regulate the flow of ingesta from reticulo-rumen to omasum
Secondary contraction
During second contraction of the reticulum, the rumen starts contracting from the dorsal sac of the rumen as caudally moving contraction towards caudal sac.This is followed by caudally moving ventral sac contractions.
Then the dorsal and ventral sacs show cranial moving contraction called the primary cycle. It is involved in mixing of ingesta and separation of large and small particles.
Secondary contractions is cranially moving begin from the caudo-dorsal blind sac moving over the dorsal sac.
The function of the secondary contraction is to expel the gases out of the rumen.
The reticulo-rumen contractions occur at a frequency of 1 to 3/ min. It is increased during eating.
During rumination, triphasic contractions occur in the reticulum in which the stronger extra contraction precedes the normal biphasic contraction.
The extra contraction in the reticulum as primary wave is referred as regurgitation contraction.
During rumination, the primary wave of the ventral sac is absent, but shows strong and prolonged ventral sac movements as secondary wave.
Nervous control of stomach motility in ruminants
Tension receptors and epithelial/mucosal receptors are sensory receptors of fore-stomach stimulated by both mechanical (coarseness of rumen material) and chemical (decrease in pH, increase in VFA ) stimuli.
Sensory afferents through vagus regulates the major contractions of rumen and reticulum.
Total vagotomy abolishes rumen and reticular contractions, rumination, eructation and reticular groove reflex.
Vagus is also the motor nerve to abomasum.
Sympathetic nerves are inhibitory to ruminant stomach, but their actions are not very important.
The intrinsic nerves of reticulo-rumen also cause weak and non cyclic contractions.
