VPB 121: Veterinary Physiology - II (2+1)

RUMINATION

• This consists of four processes
• Regurgitation
• Re-mastication
• Reinsalivation
• Redeglutition

• Rumination is a reflex initiated by mechanical stimulation of mucosal receptors of reticulum, ruminireticular fold, rumen and cardia.
• Particles of the feed influences the time on rumination.
• Feeding of hay diet requires eight hours of rumination. Feeding well chapped smaller pieces of grass  reduces time of rumination. 
• Rumination starts with third contraction of reticulum viz regurgitation contraction which aids in clearing the cardia for opening.
• Regurgitated bolus is primarily of liquid ingesta.
• From reticulum it is pushed reflexly to opened cardio oesophageal sphincter.
• Lower intra oesophageal pressure at this point causes the pressure gradient to flood the ingesta from the stomach to cardia.
• Forceful inspiration with closed glottis causes decrease in intrapleural and intra oesophageal pressure.
• The presuure gradient is purely achieved by forceful inspiratory effort mediated  by the contraction of costal muscles and not by ruminal/ reticular contraction.
• Reverse peristalsis moves the regurgitated bolus from esophagus to mouth. In the mouth, the liquid ingesta from the bolus is squeezed and swallowed. This is followed by reinsalivation and remastication.  
• Vagus provides the afferent fibres and the rumination center is located in the brain stem.
• Efferent fibres supply to salivary gland, esophagus, reticulum, muscles for inspiration, mastication and deglutition.