Week 2- 2/3 - Rumen - complete *** Flashcards
State the names of the chambers of the ruminant stomach in the order they are encountered in
reticulum
rumen
omasum
abomasum
On the gross animal, where is the rumen located?
it spans the entire left hand side of the ruminant
Describe the structural features of the Oesophagus 3
striated muscle along its length
the mucosa is insensitive
it is heavily keratinised
What is the overall capacity of the ruminant stomach?
100-250 litres
What name is given to the rumen and reticulum as a single functional unit?
- What conditions are present in the rumen? 4
the reticula-rumen
anaerobic conditions
ph of 6.5
moist
temperature 38-42 degrees
How do ruminants increase the surface area of long fibrous feedstuffs? 2
initial mastication
rumination
How often does the reticule-rumen contract?
- What is the purpose of each contraction? 2
3 times every 2 minutes
to stir, redistribute and mechanically grind ingesta
to partition fibre for re-chewing
Papillae: What stimulates the growth of Papillae? 2
- Hence, where are they longest and why?
- Where are they shortest and why?
a high concentration of volatile fatty acids
long fibre
at the top of the fluid layer where the long fibres float
at the top of the rumen where the gas cap sits
Reticulum: Describe the structure of the reticulum 4
it is a series of cells
with small conical papillae
keratinised
hexagonal appearance
Describe the appearance of the Papillae of the rumen 2
- What is their function?
- Are they all the same size?
keratinised
leaf shaped
to increase the surface area in the rumen for fermentation by flora and reabsorption
no they vary in size and shape based on diet and location
How does ingesta flow from the reticulum into the omasum?
via the reticulo-omasal orifice
Omasum: What is the function of the Omasum? 3
water absorption
volatile fatty acid absorption
pumping of ingesta form reticulum to abomasum
Omasum: How many Laminae does it contain?
- What is present on the surface of Laminae and what is the purpose of this?
- How many distinct groups do laminae form?
100
conical papillae to increase the surface area
3
Abomasum: What is the abomasum generally termed?
- What sections can it be divided into?
- In which species is it relatively larger?
the true stomach
the fundus, body and pylorus
sheep and goats
Abomasum: How many rugae does it contain?
- How do these rugae differ from other domestic species?
12 large longitudinal rugae
they are permanent even when distended
Abomasum: How is the position of the abomasum in cattle different to sheep and goats?
the abomasum has increased contact with the abdominal floor in cattle
Abomasum: What is the PH here?
- Describe the contractions
- Describe the pyloric sphincter
3-4
weak and rhythmical
there is no pyloric sphincter, only a wall thickening that acts like a valve
Neonates: Where is milk digested?
- Describe how milk is digested 4
in the abomasum
fundic glands secrete renin
this coagulates the casein in milk in the acidic environment
the clots formed retain the milk allowing complete complete digestion by pepsin
Neonates: Why is it important that milk goes into the Abomasum and not the Rumen?
if it enters the rumen it will ferment and cause scour
Neonates: How does milk bypass the rumen?
- Describe what happens when his structure is relaxed
- Describe what happens when this structure is contracted
the reticular groove
the oesophagus empties into the reticulo-rumen
the edges of the groove curl up and form a tunnel between the oesophagus and the reticulo-omasal orifice
Neonates: What is the reticular groove reflex stimulated by? 2
- Wha nerve stimulates it?
- What is it poorly reactive to? 2
suckling milk
noises associated with the feeding routine
the vagus nerve
drinking
stomach tubing
When does the reticular groove reflex work in adults?
- When specifically in sheep?
- When specifically in cattle?
when dehydrated via ADH
drenches containing copper
drenches containing sodium salts
Weaning: What prompts the development of the rumen in young animals?
- How long after birth is the rumen functional?
the presence of forage in the rumen
6-8 weeks
Why do ruminants require microbial fermentation prior to normal digestion? 3
because the food they consume consists of many beta linked polysaccharides
they lack the enzyme required to break these bonds to access the nutrients
so require microbial fermentation as some microbes secrete this enzyme
Describe what happens when ingesta enters the reticulum from the oesophagus 2
the ingesta enters the reticulum
it mixes with rumen fluid and is prepared for the anaerobic conditions of the rumen
How is the ingesta prepared, in the reticulum, for the anaerobic conditions in the rumen? 2
the reticulum contains bacteria which respire any oxygen swallowed with the ingesta
after utilising the oxygen they switch receptors and respire anaerobically
What can the rumen be thought of as?
a large fermentation vat
What happens to the microflora if you change the PH of the rumen?
- What happens if ingesta moves through the rumen too quickly?
- What are the consequences of disrupting the conditions in the rumen?
some of the organisms will die and be washed out
some of the organisms will be washed out
you many lose organisms
leasing to poor rumen health
and poor digestibility
and poor animal health
Why are the conditions in the rumen strictly anaerobic?
because oxygen is toxic to many of the microbes in the rumen
What factors need to be maintained in order to maintain a stable microbial population in the rumen? 4
nutrients - there needs to be a consistent input of food
PH needs to be maintained at 5.5-6.5
temperature needs to be maintained at 38-42 degrees
redox - oxygen entering with food needs to be rapidly utilised to maintain anaerobic conditions
Microflora: How do different organisms differ from each other?
- How do they form a food web?
- What does this enable?
different organisms are better at metabolising different substrates and produce different products
the products produced by one organism may be the substrate for another organism
it enables fatty acids to reduce and reduce in the number of carbons until methane and co2 are produced
PH buffering: How is the PH in the rumen buffered? 2
VFAs and ammonia are rapidly absorbed through the rumen wall
bicarbonate and phosphate are secreted in large volumes in saliva
Give 2 examples of other things synthesised by rumen microbiota that benefits the animal
vitamin b12
aromatic growth factors
PH buffering: How is saliva production stimulated?
- Hence, which food types produce more saliva, and are therefore more easily buffered?
- Which food types produce less saliva and why?
by mastication and rumination
long fibrous feeds
concentrate feeds because they require less chewing
Protozoa: Describe them
- Which 2 families do most rumen protozoa belong to?
they are single cell eukaryotes
holotriches
oliogotriches
What happens when you change the diet of a ruminant? 2
- how long does this adjustment take?
- What is the problem with making sudden dietary changes?
the microbiota will adjust
the balance of organisms will change
up to 2 weeks
it can affect rumen function
Fungi: Describe their metabolism
- How do they break down ingesta in the rumen? 3
anaerobes
they colonise plant fragments
then generate hyphae which extend into the material
they release enzymes to break down the material
State 3 ways the rumen can be disrupted
acidosis
starvation
oral antibiotic therapy
Monogastric Stomach: What is the immunological function of the stomach?
- Why is there minimal microbiology in the stomach?
- Give an example of how some pathogens can affect the barrier function of the stomach
- How can the barrier function be compromised pharmacologically?
to act as a barrier to infection of the lower intestinal tract
because most bacteria is killed by the acidic PH
pathogens hiding in meat
the use of antacids
Monogastric Stomach: How can Antacids be a problem for the barrier function of the stomach? 3
they increase the PH of the stomach
so the PH may not be acidic enough to kill the pathogen
this can lower the infective dose of many organisms to just one
Monogastric Stomach: State the name of one organism of particular interest.
- Describe its structure 3
helicobacter
gram negative
twisted rod shape
flagellum
Monogastric Stomach: How does Helicobacter survive in the acidic stomach if it is not tolerant to such a low PH? 2
- From where does the bacteria obtain nutrients?
- what consequence does this have to the stomach?
- How is the damage further exacerbated?
it secretes urease which breaks down urea to ammonia
ammonia is alkaline and neutralises the gastric acid
from the tissues of the stomach wall
it causes damage to stomach tissues
ammonia is toxic to epithelial cells
Monogastric Stomach: How could you test for Helicobacter? 2
blood antibody test
stool antigen test
Carbohydrates: State examples of monosaccharides 2
- State examples of disaccharides 3
hexose and pentose sugars
sucrose, maltose, cellobiose
Carbohydrates: How can ruminants digest cellobiose?
the rumen contains bacteria which produces an enzyme to break it down and obtain the sugar
Carbohydrates: What type of molecule is cellulose? 2
- What does it contain?
- Give examples of other Homoglycans of the storage polymer kind 2
a homoglycan
structural polymer
repeating units of cellobiose
starch and glycogen
Carbohydrates: Give an example of a Heteroglycan.
- What makes it a Heteroglycan instead of a Homoglycan?
- Where is this Heteroglycan found in large amounts?
hemicellulose
it is composed of several different sugars
in grass
Carbohydrates: What are carbohydrates fermented to in the rumen?
- Give 3 examples of these
- What biproducts are formed from this microbial fermentation? 2
volatile fatty acids
acetic acid, butyric acid, propionic acid
methane and carbon dioxide
Carbohydrates: The carbohydrate enters the rumen.
- What is it initially broken down into?
- From this, what is it broken down into?
- For which volatile fatty acid are there 2 different pathways from pyruvate?
pyruvate
volatile fatty acids
propionic acid
Carbohydrates: Propionic acid
- When is pyruvate broken down into propionic acid down the most common pathway?
- What types of foods encourage this pathway?
- What is the alternative pathway called?
- When is the alternative pathway used? 2
at a normal ph
forage
the lactic acid pathway
very low ph
during rapid digestion
Carbohydrates: When is a low PH created in the rumen?
- Why is this? 4
when large quantities of readily accessible carbohydrates are consumed, often in high concentrate diets
the carbohydrate can be quickly converted into pyruvate and then volatile fatty acids
this causes the PH in the rumen to drop rapidly as it cannot absorb the volatile fatty acids quick enough to buffer this
and at a low ph the lactic acid pathway for propionic acid is more likely to be utilised, further lowering the PH as lactic acid is very strong
concentrates are less fibrous so require less chewing so less saliva containing bicarbonate and phosphate is produced to buffer the ph
Carbohydrates: What happens to the proportions of different VFAs produced as percentage concentrate increases?
the proportion of acetic acid decreases
the proportion of propionic acid increases
Carbohydrates: Which forages increase the amount of acetic acid produced and why?
- Which forages are more likely to be fermented down the propionic route and why?
older forages as they contain more cellulose and hemicellulose
younger grasses because they contain a lot more sugars
Carbohydrates: How is the fore stomach adapted for VFA absorption?
- Once absorbed, where are VFAs transported?
papillae and laminae increase the surface area of the fore stomach
to the liver
Fat: What tends to happen to fats in the rumen? 2
- What is the problem with a high fat diet?
- How can we get around this in order to increase dietary fats without compromising rumen function?
they are hydrolysed
their structure is altered to become more saturated
it will depress microbial activity
calcium fatty acid salts do not depress microbial activity and can therefore be given as fat supplements
Protein: State the 2 types of protein
- What happens to rumen undegradable protein?
rumen undegradable protein
rumen degradable protein
it passes through the rumen and is digested in the abomasum
Protein: What happens to Rumen Degradable protein in the rumen? 2
it will be broken down by organisms into amino acids
some amino acids will be further broken down to form ammonia
Protein: What happens to some of the Ammonia produced in the rumen? 6
it is absorbed through the wall of the rumen
it is transported to the liver where it is converted into urea
some urea will be excreted in urine
some urea will remain in circulation
some circulating urea will be incorporated into saliva and recycled into dietary intake
urea is converted in ammonia in the rumen
Protein: What can amino acids and ammonia be used for?
- What does this require?
making microbial crude protein
energy
Protein: Give an example of a Non-protein nitrogen that can be fed to ruminants to be made into microbial crude protein
- What must the feed containing this non-protein nitrogen also contain and why? 3
urea
lots of fermentable metabolic energy so that the ammonia made from the urea can be used to make the non-microbial proteins
if there is not enough energy available, the blood concentration of ammonia will increase
this could overwhelm the liver and create toxic circulating levels
The rumen is continuously fermenting. What is required to enable this system to continue fermenting? 4
a stable PH of 6.5
removal of gases formed
a way in and a way out
maintenance of a temperature of 38-42 degrees
How are gases removed from the rumen?
- Which gases are produced?
- How much of these gases can be produced after a large meal?
by eructation
methane and carbon dioxide
30l
Synchronicity: What 2 things does Microbial crude protein synthesis depend on?
- What happens if more protein is present than energy?
- What happen is more energy is present than protein?
the presence of protein and energy
the amount of microbial crude protein produced is limited by energy so ammonia concentration increases and the blood concentration of urea increases
the amount of microbial crude protein produced is limited by protein and the excess energy is broken down to methane and wasted
Synchronicity: Why is synchronicity important for optimal rumen function? 3
the correct balance of energy and protein in the diet enables the establishment of the optimal microbial population
this leads to optimum rumen function
and optimal production of microbial crude proteins
PH: As discussed, high concentrate diets can lower the ph of the rumen, increase the proportion of Propionic acid produced and lactic acid.
- Clinically, which 2 conditions can this cause?
acute acidosis
chronic acidosis
PH: Why is it important to keep the PH in the rumen above 6?
because a PH below 6 is too acidic for cellulose digestion
Acute Acidosis: What usually causes this?
- What clinical signs could be seen? 4
grain engorgement
signs of GI pain, lying down, uncomfortable, belly kicking
Chronic Acidosis: Which group of animals is more susceptible to this?
- What clinical signs would you expect to see? 3
- Why might production decrease?
- Why might milk fat decrease?
high producing animals fed a high concentrate diet
signs of GI pain, indigestion, loose faeces
because appetite decreases, so food intake decreases, so dry matter intake decreases
because we are not getting adequate volatile fatty acid production
Chronic Acidosis: What happens to the microflora when the PH falls? 3
the balance of rumen microflora changes
the number of viable microorganisms decreases
so the rate of digestion decreases
Bloat: When does bloat occur? 4
- What is the usual mechanism of death?
when gases are not removed from the rumen by eructation
so the gases accumulate in the rumen
this increases the size of the rumen
which applies pressure to surrounding structures including the lungs
suffocation
Bloat: What are the 2 types?
gas bloat
frothy bloat
Gas Bloat: Why does this occur?
- Give an examples of when this might occur 3
when something is blocking or hindering normal eructation
physical obstruction of the oesophagus like a potato
cessation of normal rumination due to rumen acidosis or vagal indigestion
gas is unable to reach the oesophagus when in lateral recumbency
Frothy Bloat: When does this occur?
- Why does this cause frothy bloat? 2
when the ruminant grazes pastures rich in clover
soluble proteins in the clover leaves form a gassy foam with rumen gases
gassy foam cannot be removed form the rumen by eructation so builds up
Bloat: How can you treat bloat?
by placing a cannula in the paralumbar fossa to release the gas and relieve the pressure
