Lecture 34 - Ruminant Motility and Secretions Flashcards
How can herbivores hydrolyze beta-1,4 glycosidic bonds?
Microbes in their GI tract that produce cellulase and allow the animal to use short chain volatile fatty acids
Where does fermentation occur in dogs and humans?
Large intestine
What kind of GI tract will an animal have that makes fermentation valuable?
A larger fermentation vat
What is the difference between ruminants and hind gut fermenters?
Ruminants have a large, multi-compartmented section of the GI tract between the esophagus and true stomach.
Hind-gut fermenters have a specialized large intestine.
What are the functions of the liver, pancreas and gall bladder in ruminants?
Liver: stores carbohydrates, produces bile, metabolized carbohydrates, proteins and fat
Pancreas: Hormone and digestive enzyme secretion
Gallbladder: Bile storage
What do ruminants have instead of upper incisors?
Dental pad
What kind of teeth do ruminants have?
Hypsodont
What is different about the saliva of ruminants vs non-ruminants?
pH is usually higher in ruminants to neutralize and buffer acids produced during bacterial fermentation
What type of peristalsis in the esophagus do ruminants use?
Antegrade and retrograde
What type of muscle is in the entire esophagus?
Striated skeletal
Which stomach compartments make up the forestomach?
Rumen
Reticulum
Omasum
Which stomach compartment is the true stomach?
Abomasum
What is the function of the rumen?
-Storage of food
-Fermentation by microbes (bacteria, fungi, protozoa)
What is the ideal pH in the rumen and why?
~6.7
Microbes are healthiest at this pH and will start to die below 5.5 (acidosis)
What is the function of the reticulum?
-More storage of feed
-Microbe fermentation
What is the function of the omasum?
-Absorbs water and nutrients
-Prevents passage of large particles through the digestive system
What is the function of the abomasum?
Digest protein from feed and ruminal microbes
What is the pH in the abomasum?
2-3
What are the functions of the small intestine?
-Enzymatically break down nutrients
-Absorb nutrients (fatty acids, sugars, amino acids) and water via intestinal villi
What are the functions of the large intestine?
-Absorb, recirculate and conserve water
-Mineral absorption
What are 3 distinct types of contractions that occur in the rumen and reticulum?
-Mixing of ingesta wth bacteria
-Regurgitation of contents for further chewing
-Removal of gases produced by fermentation
What are the 3 layers in the rumen?
Gas cap (dorsal)
Raft
Rumen liquors (ventral)
What is the gas cap?
A pocket of gas in the top of the rumen composed of CO2 and methane produced during fermentation
What is the raft layer in a rumen?
Longer forage particles from recent ingested material
What is in the rumen liquor layer?
Finer particles released from forage breakdown from older ingested material
Does ingested material form layers in smaller ruminants?
Not really
What is the purpose of mixing contractions in the rumen?
-Move material from rumen to reticulum
-Bring microbes in contact with new feed
-Reduces flotation of solids
How do the raft and liquor move in relation to each other?
Opposite directions
How many complete rumen motility cycles happen every 2 minutes normally?
3
How is rumen motility controlled?
-Enteric nervous system
-Input from vagal efferents
-Vagal afferents (stretch receptors and chemoreceptors)
What happens if the vagus nerve is cut?
Coordinated reticuloruminal motility will be interrupted
How can diet type influence contractions?
Animals on a high roughage diet will have more frequent contractions than those on a diet rich in concentrates
How is material regurgitated?
Contraction at the mid-dorsal rumen with some elevation of ventral rumen pushes the gas cap caudally and the raft towards to cardia. The esophageal sphincter relaxes and a bolus of raft enters the esophagus and is pushed up by retrograde peristalsis
How long is one regurgitated cud usually chewed for before being swallowed?
1-2 mins
How many hours a day does an animal usually spend ruminating?
~8 hours a day during rest
How much gas is produced per hour in the rumen of an adult cow?
30-50 litres
What are the main gases produced?
CO2 and methane
Why must cows have an eructation reflex (burping)?
To avoid bloating
How is the eructation reflex carried out?
Contraction of the caudodorsal rumen pushes the gas cap towards the cardia and the ventral sac relaxes, allowing the fluid level to fall below the cardia. Esophageal sphincter opens when it detects gas and gas is pushed out by reverse peristalsis
What is frothy bloat?
Waxy substances in plants form frothy bubbles when churned in the rumen, which can’t escape as gas and inflates the rumen. This can cause issues with respiration.
What is the reticular groove reflex in neonates initiated by?
Suckling action and the presence of milk proteins and electrolytes cause pharyngeal afferent neuronal pathways to initiate this reflex
What is the reticular groove reflex?
The esophageal groove moves dorsally that guides liquids to the omasum and abomasum to be digested enzymatically (fermented milk is an ick!)
What is the milk curdled by in the abomasum?
Rennin
What happens as the calf ages and develops a population of rumen bacteria?
The reticular groove reflex shunts the high-quality proteins of milk to the abomasum to supply essential amino acids to the calf rather than to the rumen bacteria
How much saliva is produced in an adult cow daily?
100-180L
What is the function of saliva?
-Liquid for the microbes
-Buffers the rumen contents and increases pH to ~8.5 when chewing
-Lubricate food
What is different about abomasal secretions in ruminants?
It secretes lysozyme that breaks down bacterial cell walls to use it as protein. Non-ruminant stomachs don’t do this
Why is the ruminant GI system important?
-They can use resources that many other animals can’t
-Use land that can’t be used for crop production
