Rumination

()Map ALIMENTARY SYSTEM (Map) THE RUMEN

Introduction

Rumination is the process of digestion in the ruminant. It involves three simplified processes. the first is regurgitation which increases the surface area of food particles for digestion through further mechanical breakdown. The second is re-mastication and the third reinsalivation. Reinsalivation increases the volume of saliva produced whilst chewing and allows minerals to be recycled.

Process

Diagram of ruminating contractions - Copyright RVC 2008

• Reflex initiated by mechanical stimlation of the receptors in the mucosa of the reticulum, ruminoreticular fold and cardiac area of the rumen

• Frequency of contractions depends on the animal's activity
• E.g. Cattle fed on hay or straw have the most frequent contractions at 79-100 per hour during feeding, 55-76 per hour during rumination
• E.g. Cattle that are resting (not feeding or ruminating) only have contractions 47-80 per hour

• Discrete reticular contraction preceedes biphasic ruminal contraction (see ruminoreticular contractions)

• Rumination depends upon the coordination of the stomach movements with the thoracic wall and throat

• Associated with inspiration against a closed glottis creating a negative pressure in the thorax allowing ingesta to be drawn into the oesophagus

• Ingesta carried orally via an antiperistaltic wave

• Controlled by rumination centres in the hypothalamus

• Fibre increases stomach motility

• Increase in volatile fatty acids decrease stomach motility

Function

• Decrease particle size

• Increase surface area for microbial digestion

• Breaks down impervious plant coatings

• Mixes food

• Courseness of the ration influences the amount of time spent in rumination
  • Cattle ruminate for up to 10 hours per day
  • E.g. Hay diet spends roughly 8 hours per day ruminating
  • E.g. Ground dried grass diet spends roughly 5-9 hours per day ruminating
  • E.g. Concentrate diet spends roughly 2.5 hours per day ruminating