Ruminant digestion Flashcards
What is the function of a ruminant’s complex stomach?
utilize CHO sources (cellulose)
produce food and other products using CHO
What is the progression of food through the digestive system of a ruminant (9 steps)
- mouth
- esophagus
- rumen
- reticulum
- omasum
- abomasum
- small intestine
- cecum
- large intestine
what is unique about ruminant dental anatomy
there are no upper teeth, they instead have a hard dental pad
what is the function of the mouth in ruminants
reduce particle size by teeth grinding
What are the two functions of saliva in ruminants?
- moisten food
- provide buffer for the rumen
name the three VFAs produced by the microorganisms in the rumen
- acetate
- proprionate
- butyrate
the esophagus in ruminants functions in ______
both directions for rumination
The rumen can make up ___% of the body weight of an animal
20%
compared to monogastrics, the abomasum can be considered ______
true or glandular stomach (lined with mucous membrane and producing gastric juice)
The rumen and reticulum can together be considered ______
the forestomach
What is the name for the type of tissue that lines the rumen and reticulum (forestomach)
stratified squamous epithelium
Does stratified squamous epithelium have any secretions?
no
What is the function of the rumen?
- act as the site of anaerobic and microbial fermentation
- absorption of fermentation end products (VFAs)
- store food (consuming large amounts to digest later)
What is the name of the shunt that allows milk to pass directly from the esophagus to the omasum?
esophageal or reticular groove
What do you know about the development of the rumen microbiome?
at birth, the rumen is sterile, and is partially developed by 4-6 weeks
The rumen is covered with ______ that help increase _______
papillae, surface area
the appearance of the papillae can change based on….
diet and season
What is distinct about the appearance of the reticulum?
it has a honeycomb pattern
What is the function of the reticulum?
- site of microbial action and absorption of VFAs
- the pacemaker for rumen contractions
the reticulum is where ____ can occur
rumination
What is rumination?
regurgitation, remastication, resalivation, and reglutition (reswallowing)
What is the appearance of the omasum?
long, pagelike lamina
What is the function of the omasum
the function is unclear - however some water and VFA absorption occurs, and some mechanical digestion occurs
it regulates particle size flowing from the abomasum to the SI
what are the secretions of the abomasum?
pepsin, HCl, and mucin
postgastric fermentation occurs in the ____
cecum and colon
5-15% of cellulytic digestion occurs ______
in the cecum and colon
What do you know about the ruminant large intestine?
any microbial protein made here is lost in feces, but VFAs can be absorbed through the large intestine
water is also absorbed here
Why is the rumen an ideal place for microbial growth? (9)
- warmth (101-105 degrees)
- moisture
- continuous inflow of nutrients via animal eating
- pH controlled (via saliva)
- no exposure to light
- mixing via digestive turbulence
- oxygen free (anaerobic environment)
- all end products are removed (absorbed or passed) preventing waste buildup
- small particle size due to rumination
the microorganisms and the rumen and the ruminant live in ______
symbiosis
Bacteria of the rumen
- digest cellulose, starch and proteins
protozoa of the rumen
prey on bacteria, 35 species
yeast of the rumen
not a large amount, aid in cellulose digestion
in the rumen, starches and fibers are turned into ____
VFAs
in the rumen, proteins are turned into….
amino acids, then NH3, then microbial protein
in the rumen, unsaturated fats are fermented into _____
saturated fats
What are the six end products of fermentation
- VFAs
- microbial protein
- ammonia
- gas (methane and CO2)
- heat
- lipid alterations
What are the three VFAs?
- acetate (2 carbons)
- proprionate (3 carbons)
- butyrate (4 carbons)
remember APB
What is the primary site of VFA absorption?
the rumen
What is one side effect of a concentrate diet?
rumen acidosis - decimation of microbiome due to pH changes
concentrate diets produce
100-120 mmol/L of VFAs (more than forage)
5.5-6.0 pH (more acidic than forage)
forage diets produce
60-80 mmol/L of VFAs (less than concentrate)
6.5-7.0 pH (more basic than concentrate)
What is the ratio of VFAs on a forage diet?
65% acetate
20% proprionate
12% butyrate
an acetate:proprionate ratio of 3.5:1
What is the ratio of VFAs on a concentrate diet?
45% acetate
35% proprionate
15% butyrate
an acetate:proprionate ratio of 2:1 or less
The VFA ratio can be altered by…
feeding ionophores (increases daily gain, efficiency and fertility) - works by shifting microbiome to organisms that make proprionate
most common brands rumensin and lasalocid
increasing the percentage of proprionate produced by a ruminant….
increases average daily gain, increases feed efficiency, and increases fertility
What happens to proteins in the rumen?
proteins are either fermented or escape the rumen
This compound can be utilized by bacteria to produce microbial protein
urea/ammonia
What are the components that protein can be broken into in the rumen?
- urea (MCO protein)
- carbon skeleton (VFAs)
What happens to excess ammonia in the rumen?
NH3 leaves the rumen and is recycled (as a buffer)
Cattle can get _____% of their crude protein from microbes
50% CP
Which other important nutrients are synthesized by microbes in the rumen?
- B vitamins
- Vitamin K
- essential fatty acids (ruminants do not require fatty acids)
Excess NH3 is often lost in the ______
urine
Why are ruminants energetically inefficient compared to monogastrics?
gases produced from fermentation cause some energy to be lost
What happens to lipids in the rumen?
microbes saturate unsaturated fatty acids
Why is excess fat bad for ruminants?
Ruminants must have >10% fat in their diet because excess fat decreases fiber digestion - it coats the feed and hinders microbial attachment and degradation of cellulose
fats are _____ times more energy dense than other macors
2.25
Ruminantion is the set of steps that _____ digesta for passage to the lower digestive tract
reduce
regurgitation
bolus is moved by reverse contraction of the esophagus from rumen to mouth
remastication
reduction of particle size via mechanical digestion
resalivation is important because..
saliva acts as a buffer in the rumen, and nitrogen can be recycled here
reglutition
reswallowing the remasticated food
eructition
the process of removing gas from the rumen
Which 4 gases are produced via fermentation in the rumen?
- H2
- CO2
- CH4 (methane)
- H2S (hydrogen sulfide)
As the rumen contracts, gases are forced ____
backwards, then forwards and out the esophagus
Bloat is often caused by ______
an inability to eructate
What inhibits eructition in cattle, causing bloat?
froth or foam in the rumen
What are the symptoms of bloat in cattle
- distension of left (rumen) side
What is the cause of bloat in cattle
- consumption of very rich food very fast (barn door open)
- legumes (high in soluble protein)
How can bloat be treated? (3)
- trochar
- ionophores
- poloxaline (bloat guard)
excess H2 in the rumen can _____
inhibit the fermentation process
methanogen
anaerobic archaea that create methane from CO2 and H2 - thus limiting H2 in the rumen
Most excess gases in the cow are _____ out
burped (eructated)
How long does CH4 live in the atmosphere?
12 years
The most common form of rumen acidosis is called
lactic acidosis
What is the most common cause of rumen acidosis?
High amounts of concentrate in the diet
Why does rumen acidosis occur (5)
- rapid increase in grain in diet
- rapid change from forage to concentrate
- barn door left open situations (cows get into rich food)
- grazing residue crop (high value leftovers are preferred by cattle, causing acidosis)
- improper ration balancing and/or management
What might cause a large increase in lactic acid producing bacteria in a ruminant?
increased starches in the diet (CHO)
decreased pH causes microbiome imbalance, allowing one kind of bacteria to colonize
Symptoms of rumen acidosis
- lashing tail
- DRHA
- decrease of intake (off feed)
- abdominal pain
- dehydration
- laminitis
What physiological changes might happen due to rumen acidosis (3)
- lowered blood pH
- keratinization of rumen wall
- influx of water into rumen, dehydration and damage to rumen wall due to osmotic imbalance
How to prevent rumen acidosis?
- have adequate roughage in the diet
- change animals to new diets slowly
- feed buffer
- use antibiotics (also prevents liver abcesses)