The Rumen

Question 1

Name the 4 stomachs in a rumen

Answer 1

Reticulum, Rumen, Omasum and Abomasum

Question 2

On what side of the ruminant does the rumen sit?

Answer 2

LHS

Question 3

Describe the internal surface of the rumen?

Answer 3

Villi projections for increased SA absorption

Question 4

Describe Rumen-Reticulum motility

Answer 4

Primary A Cycles - mixing cycle every 1-2 minutes, diphasic contraction of reticulum and monophasic contraction of dorsal sac then ventral. Contraction waves moves cranial to caudal
Secondary B Cycles - Eructation cycles, every 1-2 minutes resulting in erucation of gas from rumen. Rumen dorsal wall contracts then the ventral sac -> pushes gas into cardia and leads to eructation.
Regurgitation - additional contraction -> reticular contraction flooding cardia, pressure change and material is propelled forward and an anti-peristaltic wave in oesophagus transfer the bolus to the mouth.

Question 5

What three areas can the abomasum be divided into?

Answer 5

Fundus, body and pylorus

Question 6

What type of epithelium will you find in the abomasum?

Answer 6

Columnar epithelium

Question 7

Explain how neonatal ruminants digest milk

Answer 7

Milk is digested in the abomasum. Rennin is produced by the fundic glands where coagulating the casein, allowing pepsin to digest the milk.
Milk is taken from the mouth to the absomasum bypassing forestomch through the OESOPHAGEAL GROOVE or RETICULAR GROOVE -> takes milk from oesophagus into omasal canal into abomasum. This is muscular reflex stimulating by sucking and feeding routine.

Question 8

Name the different sections of the rumen as viewed from the LHS

Answer 8

Dorsal sac, dorso-caudal blind sac, ventro-caudla blind sac, cranio dorsal blind sac, reticulum and rumenoreticular orifice.

Question 9

What are cellulose molecules held together by?

Answer 9

Beta-1,3-glucosidases

Question 10

Name the 6 sources of pyruvate for bacteria in the rumen

Answer 10

Strach (Maltose), Cellulos (cellobiose), Pectins, Hellicellulose, Sucrose and Fructans.

Question 11

Name the 3 VFA’s produced by bacteria

Answer 11

Acetate
Butyrate
Propionate

Question 12

Describe the pathway for acetate and butyrate production

Answer 12

Glucose -> Pyruvate -> Acetyle-CoA -> Acetate

Question 13

How is acetate used for energy production in cows?

Answer 13

It is comverted to Acetyl-CpA where in can be converted into M-CoA and used in fat production or is used in the oxidative phosphorylation cycle (TCA cycle)

Question 14

How is butyrate used as an energy source in cattle?

Answer 14

Butyrate -> butyric acid, Beta-3 hydroxbutyrale -> Acetyl-Coa in TCA cycle or fat storage

Question 15

How is Propionate produced and used in the rumen?

Answer 15

Produced from glucose -> pyruvate -> propionate
Provides the GLUCOSE for the ruminant through gluconeogenesis:
Propionic acid -> succinyl-CoA -> Phosphoenolpyruvate -> Glucose (TCA or Stored)

Question 16

How are VFA absorbed by the ruminant?

Answer 16

Facilitated diffusion of VFA anions or simple diffusion of undissociated VFA’s.
70-90% is absorbed through passive diffusion down concentration gradient (maintained by active transport of Na+) in the rumen (rest is absorbed in omasum). Once across the ruminal membrane, they are carried by ruminal veins to the portal vein and hence through the liver.

Question 17

How does rumen acidosis happen?

Answer 17

When the animal suddenly eats a large amount of starch (easily fermentable carbohydrates), causes a pH drop greater than normal in the rumen due to rapid production of VFA’s. If it drops below 5, only lactate forming bacteria can thrive and the lactate converting bacteria fail to thrive. Due to poor absorption of lactate, lactate production and lack of converting, pH can get to as low as 4.
This causes damage to the epithelium, increased acid absorp[tion in digestive tract leading to systemic metabolic acidosis, and due to H+ concentration, rumen contractions can become very weak or stop. Lactic acid and VFA concentration in rumen is so great can cause osmotic flow into rumen -> dehydration.

Question 18

What can cause gas bloat?

Answer 18

Blockage of normal eructation through feed being stuck in oesophagus normally
Frothy bloat -> result of feeding on clover -> gas collects in the form of bubbles and can’t be burped out
Both cause cranial displacement of diaphragm squishing vena cava -> death

Question 19

What is the fate of rumen undegradable protein?

Answer 19

Bacteria do not have the enzymes to digest it -> digested in the abomasum and absorbed in SI.

Question 20

What is the fate of rumen degradable protein?

Answer 20

1) Bacteria break it down into peptides -> AA’s -> Microbial protein which eventually passes into abomasum and intestine
2) Majority is converted to AA’s and deaminated -> forms ammonia and VFA’s -> which are then coonverted to micrboail protein

Question 21

What happens when a ruminant eats non-protein nitrogen?

Answer 21

1) Can be deaminated to ammonia and used in microbial proteins
2) Can be converted to ammonia, taken to liver -> converted to urea exreted in the urine via the kidney
OR taken to liver -> converted to urea -> transported to salivary gland and recycled

Question 22

Give an example of an organism found in the rumen that has the ability to breakdown cellulose?

Answer 22

Fibrobqacter, Ruminococcus

Question 23

Give an example of an organism found in the rumen that has the ability to breakdown hellicellulose and Pectin?

Answer 23

Fibrobqacter, Ruminococcu, Prevotella and Butyrivibrio

Question 24

Give an example of an organism found in the rumen that has the ability to breakdown of starch and sugar?

Answer 24

Prevotella and Butyrivibrio

Question 25

Give an example of a methanogen that can be found in the rumen.

Answer 25

Methanobrevibacter ruminantium

Methanomicrobium mobile

Question 26

What two families of protozoa are present in the rumen?

Answer 26

Isotrichidae and Ophyroscolecidae

Question 27

What genus of fungi can be found in the rumen?

Answer 27

Neocallimastix

Question 28

Name 5 evolutionary adaptations herbivores have for their diet type

Answer 28

• Large volume of food intake
• Slow mixing and digestion
• Symbiotic microbial digestion (fermentation)
• High water intake
• Large fermentation chambers
• Produces lots of methane -> readily released
• Saliva can buffer the rumen
• Very coarse feed remixed several times to extract energy
• fermentation can detoxify diet components
• fermentation products easily absorbed
• Digestion completed before LI.