PHYSIOLOGY - Reticulorumen Motility

Question 1

What are the three types of rumino-reticular contractions?

Answer 1

Primary (mixing) contractions
Secondary (eructation) contractions
Rumination contractions

Question 2

What is the function of primary (mixing) rumino-reticular contractions?

Answer 2

Facilitation of the mixing of dry dietary fibre to increase its contact with buffering saliva and fermentative bacteria

Question 3

What is the main function of secondary (eructation) rumino-reticular contractions?

Answer 3

The eructation of gases that have accumulated in the dorsal sac of the rumen due to microbial fermentation

Question 4

What is the function of rumination contractions?

Answer 4

Rumination contractions facilitate the aspiration of fibre back into the oesophagus and into the mouth for re-mastication and re-salivation

Question 5

What are the steps of the primary (mixing) contraction?

Answer 5

Biphasic reticular contraction
Dorsal sac ruminal contraction
Ventral sac ruminal contraction

Question 6

What are the steps of the secondary (eructation) contraction?

Answer 6

Dorsal sac ruminal contraction
Ventral sac ruminal contraction
Caudoventral sac ruminal contraction to move the gas bubble cranially

Question 7

What are the steps of the rumination contraction?

Answer 7

An additional reticular contraction precedes the biphasic reticular contraction that occurs during the primary (mixing) contraction. During this additional contraction, the thorax expands, epiglottis closes over the larynx and retroperistaltic contractions of the oesophagus move the bolus back into the oral cavity

Question 8

Why is it so important that the gases accumulated in the dorsal sac of the rumen are eructed?

Answer 8

If these gases accumulate and are not eructed, this can cause rumen bloat, cardiovascular collapse and death

Question 9

Why is rumination so important?

Answer 9

Rumination allows for the further breakdown of the bolus, increasing its surface area for microbial fermentation. The re-mastication during rumination also stimulates parotid saliva to re-salivate the bolus. This saliva contains bicarbonate which when swallowed will neutralise the rumen pH to prevent damage to the rumen by volatile fatty acid pH