9. The rumen complex Flashcards
what is the purpose of fermentation?
- transforms forage into the simple sugars that rumen microorganisms can use for growth
- structural carbohydrates are broken down by rumen microbes
- microbes ferment forages and produce volatile fatty acids which is a major energy source
what percentage of energy can herbivores derive from microbial breakdown?
70%
what volatile fatty acids are essential in the rumen complex?
- butyrate
- propionate
- acetate
what re the 3 stages of rumen development?
- pre- ruminant
- transitional
- ruminant
what is the oesophageal groove?
- muscular structure
- found at lower end of oesophagus
- when closed it from a tube so milk can go directly into the abomasum
what does the oesophageal groove prevent?
milk being fermented or soured by ruminant micro-organisms
how much milk replacer should calves be fed?
5-6 litres daily: 13-15% birth weight
when do you start feeding concentrates?
from 3-4 days old
what does feeding concentrates do?
- increases butyrate and propionate
- ‘digested’ in the rumen
- increases papillae number and size (rumen absorptive ability)
- high energy (reduces gut fill)
what problems can arise from only feeding concentrates?
- hyper- keratinisation
- clumping of papillae
- decreased rumen motility
how long should you feed concentrates for?
3-4 weeks
why must concentrates be fed for 3-4 weeks?
the rumen isn’t developed enough for fibre fermentation
what are the advantages of fibre?
- stimulates rumination and saliva production
- muscular development of rumen
- increases pH
- reduces keratinisation
- increases DMI and size of rumen
- improves post weaning total DMI
- produces acetate
Where is the effect on concentrates on development of papillae most noticeable?
Dorsal and ventral sacs of rumen
how many days does it take for papillae to develop?
21
when are calves usually weaned?
4-8 weeks
what percentage of hay should be fed with concentrates?
10%
how many months does it take for rumen maturity?
4-6 months
why feed hay pre- weaning?
- promotes rumination
- muscular growth and health of rumen
- reduces acidosis
- maintains rumen pH
when is the transition period from mono gastric to ruminant?
over 4 weeks:
- 2 pre- weaning
- 2 post-weaning
Why are bacteria/protozoans needed to digest fibre?
- Fibre = carboyhydrate
- Consists of glucans which are β-linked so
can’t be digested by mammalian enzymes - Fermentation breaks the bonds.
How much bacteria, protozoa and fungi can be found in the rumen?
Bacteria: 10 billion/ml
Protozoa: 1 million/ml
Fungi: 1000/ml
which part of the stomach is glandular?
abomasum
what shape is the abomasum?
j- shaped
what side of the animal do you find the rumen?
left
how does the rumen work?
- Fermentation vat
- cycle of contractions: 1-3 a minute
- belching removes the fermentation gases
what is the main fermentation gas?
methane
how much gas is produced every hour in a cow and sheep/goat?
Cow: 30-50 litres/hour
Sheep/goat: 5 litres/hour
what does the reticulum do?
- traps large feed particles
- makes sure they don’t enter next section before they are digested
- regurgitation of ingesta
- honeycomb structure
what percentage of the rumen is water?
80%
what is the role of the omasum?
- rumen is 80% water, folds of the omasum squeeze out the water from the feed and ensures the water stays in the rumen
what happens in the abomasum?
- low pH
- enzymes digest the proteins in the feed
- AA’s then absorbed in small intestine
How does a cow swallow + regurgitate its food?
- Swallows fibre, rips up using tongue
- Regurgitates and chews (to allow it to move to an area of safety)
- ruminates until food is small enough to pass out of the rumen
- Chewing cud = smaller particle size = more SA available to micro-organisms = efficient digestion.
how much saliva does a cow produce?
150-250l
what percentage does saliva neutralise the acid produced in the rumen?
30%
what is the pH of saliva?
8.2
what percentage of life do cows spend ruminating?
30%
what are the food layers in the rumen?
- Layer of gas on top formed from fermentation
- Plant fibres (large particle size)
- ‘Soupy’ layer (fibre = smaller particle size)
- Very small fibre particles + cereals (ready to exit to omasum).
What happens to plant carbohydrates in the rumen?
- Bacteria bind to fibre + carbs broken down to smaller molecules
- Glucose + monosaccarides released - absorbed by bacteria
- Glycolysis releases pyruvate
- Pyruvate is oxidised to VFAs.
How is plant protein digested in the rumen?
- bacteria bind to fibre - plant cell was and the protein Is broken down to small peptides
- broken down to Amino acids which is used by bacteria. Most deaminated to ammonia and VFA
- ammoni and VFA used to make bacterial protein
- bacteria pass into small intestine, protein digestion provides amino acids for the cow
what does rumen degradable protein (RDP) do?
- feeds rumen bacteria
- ensures adequate supply of microbial protein
what does rumen undegradable protein (RUDP) do?
- passes through the rumen unchanged
- digested in small intestine
