Rumen fermentation

What are the simple carbohydrates?

1. monosaccharides

2. oligosaccharidies - disaccharides and trisaccharides

bold = clinically relevant

what are homoglycans?

• polysaccharide carbohydrate

what do homoglycans form?

• glucans

• pectin

• hemicellulose

• hyaluronic acid, chondroitin

• gums, mucilages

what are the important glucans?

Structural = cellulose

Storage = starch, glycogen, dextrins (intermediate of starch and glycogen)

what is hemicellulose?

• alkali soluble heteroglycan

• mixture of pentoses and hexoses

What is the pathway of starch metabolism in ruminants?

Starch → maltose or isomaltose → glucose → glucose-1-P → glucose 6-P → fructose 6-P → pyruvate

what is cellulose metabolism in ruminants?

startch → cellbiose → glucose → xyz → pyruvate

what is the pathway of pectin metabolism?

pectin → pectic acid → cgalacturonic acid → xylose → xylose-5P → fructose-6P → pyruvate

what is the metabolism of hemicellulose?

hemicellulose → xylobiose → xylose - xylose-5P → fructose -6P → pyruvate

how are fructans metabolised?

fructans → fructose → fructose 6P → pyruvate

what is the goal of carbohydrate metabolism?

• pyruvate

what does pyruvate go on to produce?

• VFAs

what are 5 important products of carbohydrate digestion

1. methane

2. acetate

3. proprionate

4. butyrate

   1. CO2

how does VFA production alter?

• with diet type

what do older forages have more of?

• higher acetate

how are nutrients absorbed in the forestomach?

• active transport of Na+ → cotransport

• VFAs are rapidly absorbed and transported to liver for processing

• ions are absorbed and recycled

where does most VFA absorption take place?

• reticulorumen

how is fat digested?

• very limitedly

• tend to hydrolyse it and alter

• get more saturated fat as a result

• only short chained fatty acids are absorbed

how does a high fat diet affect the microbiota?

• depresses their activity

what does protein synthesis require?

• energy

how is excess ammonia disposed of?

• urea → salivary glands or kidneys

what happens to undegradable protein in the rumen?

• goes to small intestine and abomasum → further digestion to then be absorbed

what is MCP?

• microbial crude protein

how important is MCP for ruminants?

• very

what are all microbiota capable of with protein?

• synthesising all essential amino acids

how is good quality protein affected?

• made poorer unless protected or not rumen degradable but absorbable

how are poor quality proteins/NPN affected?

• made better

• NPN = non protein nitrogen

how can we feed NPN? non-protein nitrogen?

• feed along with a high energy feed - FME - fermentable metabolic energy

or

• distributed in feed during day - fed at a steady rate

why do we need to avoid over consumption of NPNs?

• liver becomes overwhelmed → toxic levels in circulation

what does rumination promote in the mouth?

• saliva production

what is eructation?

• expulsion of excess gas

why is rumen synchronicity essential?

• if we don’t balance presence of nutrient with energy available, the production of desired product is limited

• if more E is present than nutrient → E is lost to methane production

for what nutrient is rumen synchronicity essential?

• protein

what happens if rumen pH becomes too low? what is it due to?

• we get acidosis

• due to lactic acid build up

how does acute acidosis present?

• lethargic

• may become bloated

• tachypnoeic?

why do we see acute acidosis?

• usually due to grain engorgement

what is often the outcome for acute acidosis?

• death

what do we need to give to counter acute acidosis?

• antacids

why do we get chronic acidosis?

• high producing animals are fed concentrate

what do we see with chronic acidosis?

• reduced feed intake

• pain

• indigestion

• loose faeces

• low milk fat levels

what is the knock on effect of pH change in the rumen?

• rate of digestion decreases due to loss of microorganisms

• proportion of different VFAs produced changes

what condition do we see when eructation can’t occur?

• bloat

what often kills the animal with bloat?

• expansion of rumen → compressed diaphragm → reduced thoracic space → lungs can’t expand → asphyxiation

why do we get gas bloat?

eructation is blocked:

1. physical obstruction

2. cessation of normal rumination

3. gas is unable to reach oesophagus

why is sheep on their backs so dangerous?

• can’t eructate → bloat → asphyxiation, same reasons as for cattle

why may we get frothy bloat?

• pastures rich in clover

How do we correct bloat?

• trochlear and canula in the left flank

How does camelid GIT structure differ from a ruminant?

• has 3 compartments: C1,C2 and C3

• have a unique forestomach that lacks a distinct reticulum

• no significant omasum - C3 functions similarly to it

Aspect	Roughage diet	Concentrate diet
Fermentation characteristics
Rumen pH
Microbial population
Rumen motility

complete the table

Aspect	Roughage diet	Concentrate diet
Fermentation characteristics	Slower fermentation due to complex plant materials	Faster fermentation with higher E concentration
Rumen pH	Higher and more stable pH	Lower and more variable pH
Microbial population	Well-adapted to fibre digestion	Shift towards microbes that thrive on simple carbohydrates
Rumen motility	Higher motility due to need for continuous mixing	Decrease as diet is more easily digested

.	Advantages	disadvantages
ruminant
Non-ruminant

Complete the table

.	Advantages	disadvantages
ruminant	Efficiently use fibrous plant materials  Produced VFAs by microbial fermentation  Use lower quality foliage  Rumen microbes synthesise certain vitamins	Methane production contributes to greenhouse gas emissions  Risk of bloat
Non-ruminant	Faster digestion and nutrient absorption  Less methane production  Simple stomach allows for complex/diverse diet  No risk of bloat	Insufficient use of fibrous plant materials  Limited ability to digest cellulose

what is the mucosa sstructure in the C1 and C2 of a camelid?

• non-papillated squamous epithelium an glandular within saccules

where in the camelid is the true stomach?

• last fifth of the C3