What cycle is the main eructation cycle?
When does erructation occur?
At the end of the caudal to cranial contraction of the ventral sac
Explain the secondary cycle
Moves gas in rumen towards cardia
Animal inhales and creates negative pressure in thorax which draws gas into esophagus
Cranial to Caudal movement in ventral sac then caudal to cranial movement in dorsal sac
Microbes produce gas
Gas build up occurs in dorsal rumen
Secondary contraction moves gas to the cardia region of reticulum
Gas causes reflex opening of cardia and caudal esophagus
Animal inhales creating negative pressure in thorax drawing gas into esophagus
Some gas exhaled directly some enters lungs to be exhaled on next breath
What can occur to gas during eructation
Can be absorbed into blood
ie. ketones in blood
What feed increases rumination?
- have to break it down more
WHat is rumination and indicator of?
What is released during rumination?
Sequence of events of rumination
Just before primary contraction, reticulum contracts
Negative pressure created by inhalation while airways are closed
Cardia and distal esophageal sphincter relax, drawing cud into esophagus
Esophagus contracts cranially (rvs peristalis) cud travels toward mouth
Tongue raised and squeezes fluid out of cud and fluid swallowed
Solid cud is chewed for 10-60sec
Two outcomes of rumination
Buccal receptor stimulation
- increased salivation and rumen movement
- More mixing of ingesta
Smaller particle size
- Greater surface area for microbes
- Greater chance of passing omasum
5 Ways to examine rumen motility
Examine rate and strength of contractions
What do we look for upon a visual exam
See undulations of L. Paralubar fossa
Look for bloat
What do we ausculatate for?
Loud primary cycle
Fluid Splashing - Occurs at onset of bloating
Tinkling or tinging - definite indication of bloat
What do we externally palpate for
Doughy feel = healthy
What do we feel for upon rectal examination?
Feel caudodorsal rumen contractions
What is hypomotility?
Less than normal motility
What is atony or stasis?
Distinguish between primary and secondary clinical signs
Primary - something wrong with rumen
Secondary - Other part of body in pain
5 mechanisms of decreased motility
Direct Depression of gastric center
Decrease stimulatory inputs from peripheral receptors to gastric center
Increase inhibitory inputs from peripheral receptors to gastric center
Failure of neuromuscular transmission
Increased sympathetic stimulation
10 Conditions causing decreased motility
Animal is not eating
What receptors does lack of eating affect to cause decrease in rumen motility
Decrease in buccal mechanoreceptor stimulation
Decrease reticulorumen tension receptor stimulation
Decrease epithelial receptor stimulation, decreases rumination
How does an LDA or RDA decrease rumen motility?
Abomasum distended with air or fluid
Stimulation of abomasal tension receptors
Incrases inhibitory inputs to gastric centre
All of this causes pain
What is hardware disease also known as?
How does traumatic reticuloperitonitis cause a decrease in rumen motility?
Direct depression of gastric center
- Acute phase proteins (inflammation and fever)
- Lack of appetite
Two types of bloat?
Free gas bloat
Explain free gas bloat
Failure to eructate
Not an overproduction of gas
Typically due to something blocking esophagus
How does bloat decrease rumen motitily?
Increase inhibitory signals to gastric centers from epithelial receptors
What is frothy bloat
More common than free gas
Some legumes and alfalfa cause formation of froth
- gas produced by bacteria remain trapped in solution
Froth covers cardia
Inhibits eructation reflex
Explain rumen impaction
Common in Sk
ingestion of large quantities of poor quality or indigestibel feed (ie straw)
Leads to rumen distension
How does rumen impaction decrease rumen motility
High rumen pressure, increases inhibitory signals to gastric center from epithelial receptors
Explain ruminal acidosis
CHO engorgement (grain overload)
More lactic acid produced, pH drops
How does Ruminal acidosis decrease rumen motility?
Increase inhibitory signals to gastric centre from epithelial chemoreceptors
Explain hypocalcemia (milk fever)
Common periparturient disease of dariy cows
Low plasma (extracellular) calcium
How does hypocalcema cause decreased rumen motility?
Failure of Neuromuscular transmission
- Impulse transmission down vagal nerve is depressed
- extracellular Ca needed for ACh release from axon into synaptic cleft
Rumen/Reticulum smooth muscle requires Ca for contraction
What occurs in downer cow?
Inappetant - decrease gastric sitmulation
Fluid covering cardia - decrease eructation
With respect to rumen motility, what is the vagus nerve responsible for?
What does a vagotomy do?
Stops motility, rumination and eructation
How does Stress/fear decrease rumen motility?
Increases sympathetic response
- Splanchnic nerve inhibits motiliyt
Affect of atropine on rumen motility?
Competitive ACh antagonist
- blocks parasympathetic transmission at post-synaptic receptors (vagal nerve)
Can drugs be used to treat rumen stasis?
No, dont treat for rumen immotility, find out what is causing the problem