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

MECHANISM AND NERVOUS CONTROL OF RUMINATION

• Rumination
  • It is the process of bringing back the cud from the rumen and reticulum to the mouth for further chewing.
• Regurgitation
  • The cud that returns to the mouth is mainly the liquid from the rumino reticulam. 
  • The regurgitated cud consists of small particulate matter highly mixed with liquid and in advanced stage of fermentation.
  • Freshly eaten forages whose particle size is too great to be suspended in the rumen fluid  for extensive maceration and are not regurgitated.
  • The glottis is closed by the elevated soft palate and inspiratory effort with tongue causes a drop in intra-thoracic and intra-oesophageal pressure.
  • The cardia and caudal oesophageal sphincter get open, simultaneously extra-reticular contractions force the cud from the retuculum into the oesophagus due to negative intra-thoracic pressure.
  • An antiperistaltic wave of oesophagus carries the cud to mouth.
• Remastication
  • In the mouth, the liquid portion of the cud is squeezed and swallowed. The remaining solid mass is chewed with slow, regular chewing movements for about 40-seconds.
• Reinsalivation
  • During the process  of remastication saliva is added from parotid gland followed by reswallowing
• Redeglutition
  • It is the act of reswallowing of the cud
  • Time spent in rumination varies in different animals and with different rations.
  • Average daily duration for rumination in cattle is 10 hours on hay diet.
  • The proportion of grain and roughage in ration influences rumination time.
  • With low roughage diets or  finely ground roughage,total rumination time may be reduced to 3 hours/ day.
  • Peak rumination occurs during afternoon and in the middle of the night.
• Nervous control of rumination
  • Rumination is a reflex act, but it can also be influenced by voluntary control.
  • The receptors for rumination are in the reticular wall, cranial pillars of rumen and rumino-reticular fold.
  • Vagus provides afferent nerve fibres to the rumination centre in the medulla.
  • The efferent nerves are the motor nerves controlling muscles of larynx, oesophagus, and reticulum.