9. The rumen complex

Question 1

what is the purpose of fermentation?

Answer 1

• 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

Question 2

what percentage of energy can herbivores derive from microbial breakdown?

Answer 2

70%

Question 3

what volatile fatty acids are essential in the rumen complex?

Answer 3

• butyrate
• propionate
• acetate

Question 4

what re the 3 stages of rumen development?

Answer 4

• pre- ruminant
• transitional
• ruminant

Question 5

what is the oesophageal groove?

Answer 5

• muscular structure
• found at lower end of oesophagus
• when closed it from a tube so milk can go directly into the abomasum

Question 6

what does the oesophageal groove prevent?

Answer 6

milk being fermented or soured by ruminant micro-organisms

Question 7

how much milk replacer should calves be fed?

Answer 7

5-6 litres daily: 13-15% birth weight

Question 8

when do you start feeding concentrates?

Answer 8

from 3-4 days old

Question 9

what does feeding concentrates do?

Answer 9

• increases butyrate and propionate
• ‘digested’ in the rumen
• increases papillae number and size (rumen absorptive ability)
• high energy (reduces gut fill)

Question 10

what problems can arise from only feeding concentrates?

Answer 10

• hyper- keratinisation
• clumping of papillae
• decreased rumen motility

Question 11

how long should you feed concentrates for?

Answer 11

3-4 weeks

Question 12

why must concentrates be fed for 3-4 weeks?

Answer 12

the rumen isn’t developed enough for fibre fermentation

Question 13

what are the advantages of fibre?

Answer 13

• 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

Question 14

Where is the effect on concentrates on development of papillae most noticeable?

Answer 14

Dorsal and ventral sacs of rumen

Question 15

how many days does it take for papillae to develop?

Answer 15

21

Question 16

when are calves usually weaned?

Answer 16

4-8 weeks

Question 17

what percentage of hay should be fed with concentrates?

Answer 17

10%

Question 18

how many months does it take for rumen maturity?

Answer 18

4-6 months

Question 19

why feed hay pre- weaning?

Answer 19

• promotes rumination
• muscular growth and health of rumen
• reduces acidosis
• maintains rumen pH

Question 20

when is the transition period from mono gastric to ruminant?

Answer 20

over 4 weeks:
- 2 pre- weaning
- 2 post-weaning

Question 21

Why are bacteria/protozoans needed to digest fibre?

Answer 21

• Fibre = carboyhydrate
• Consists of glucans which are β-linked so
  can’t be digested by mammalian enzymes
• Fermentation breaks the bonds.

Question 22

How much bacteria, protozoa and fungi can be found in the rumen?

Answer 22

Bacteria: 10 billion/ml

Protozoa: 1 million/ml

Fungi: 1000/ml

Question 23

which part of the stomach is glandular?

Answer 23

abomasum

Question 24

what shape is the abomasum?

Answer 24

j- shaped

Question 25

what side of the animal do you find the rumen?

Answer 25

left

Question 26

how does the rumen work?

Answer 26

- Fermentation vat - cycle of contractions: 1-3 a minute - belching removes the fermentation gases

Question 27

what is the main fermentation gas?

Answer 27

methane

Question 28

how much gas is produced every hour in a cow and sheep/goat?

Answer 28

Cow: 30-50 litres/hour Sheep/goat: 5 litres/hour

Question 29

what does the reticulum do?

Answer 29

- traps large feed particles - makes sure they don't enter next section before they are digested - regurgitation of ingesta - honeycomb structure

Question 30

what percentage of the rumen is water?

Answer 30

80%

Question 31

what is the role of the omasum?

Answer 31

- rumen is 80% water, folds of the omasum squeeze out the water from the feed and ensures the water stays in the rumen

Question 32

what happens in the abomasum?

Answer 32

- low pH - enzymes digest the proteins in the feed - AA's then absorbed in small intestine

Question 33

How does a cow swallow + regurgitate its food?

Answer 33

- 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.

Question 34

how much saliva does a cow produce?

Answer 34

150-250l

Question 35

what percentage does saliva neutralise the acid produced in the rumen?

Answer 35

30%

Question 36

what is the pH of saliva?

Answer 36

8.2

Question 37

what percentage of life do cows spend ruminating?

Answer 37

30%

Question 38

what are the food layers in the rumen?

Answer 38

1. Layer of gas on top formed from fermentation 2. Plant fibres (large particle size) 3. 'Soupy' layer (fibre = smaller particle size) 4. Very small fibre particles + cereals (ready to exit to omasum).

Question 39

What happens to plant carbohydrates in the rumen?

Answer 39

- Bacteria bind to fibre + carbs broken down to smaller molecules - Glucose + monosaccarides released - absorbed by bacteria - Glycolysis releases pyruvate - Pyruvate is oxidised to VFAs.

Question 40

How is plant protein digested in the rumen?

Answer 40

- 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

Question 41

what does rumen degradable protein (RDP) do?

Answer 41

- feeds rumen bacteria - ensures adequate supply of microbial protein

Question 42

what does rumen undegradable protein (RUDP) do?

Answer 42

- passes through the rumen unchanged - digested in small intestine