Rumen Diet and structure

Question 1

Herbivore diet

Answer 1

-plant based diets high in carbohydrates (not sugar), low in fat
-difficult to digest resulting in slow passage rate and fermentation

Question 2

Herbivore digestive tract

Answer 2

-longest/most complex GI tract

Question 3

Herbivore teeth

Answer 3

-adapted for grinding

Question 4

Ruminant fermentation

Answer 4

-foregut fermenters, pre gastric fermentation (before glandular stomach)
>microbial breakdown before glandular stomach

Question 5

Ruminant chambers

Answer 5

-4 chambers
-Reticulorumen
- sheep, cattle, deer

Question 6

Pseudo-ruminants

Answer 6

-3 chambers (C1, C2, C3)
-camels, llamas, alpacas

Question 7

Marsupials

Answer 7

-also have a forestomach but different structure

Question 8

Advantages of ruminant stomach

Answer 8

-microbial fermentation-able to break down fibrous plant material. Can obtain energy from cellulose (mammals can’t break beta- 1,4 linkages)
-microbial protein- can synthesize AA from non-protein nitrogen sources and can change AA profile of feed
-B-vitamins- synthesized by gut microbes
-rumination (regurgitation) allowing for increased mechanical breakdown
-fermentation products can be absorbed by SI (efficient!)
-ability for detoxification of plant compounds

Question 9

Disadvantages of ruminant stomach

Answer 9

-takes a long time (slow transit of material through gut)
-rumen capacity limits feed intake (even further reduced during late gestation)
-only small particles (2-4mm) can pass to the omasum
-lower digestibility results in lower passage rate
-takes up a lot of space (weight)

Question 10

Ruminant chambers

Answer 10

1.Reticulum
2.Rumen
3.Omasum
4. Abomasum

Question 11

Reticulum

Answer 11

-acts as a pump (directs contents)
-allows small/dense digesta particles to move to omasum
-collects large and low density digesta for rumination
-traps heavy objects (hardware disease)
-contractions form esophageal groove in neonates (milk bypasses the rumen into the omasum)

Question 12

Rumen-secretions, volume, absorption

Answer 12

-microbial fermentation
-large volume (100-225L in cattle)
-lined with papillae for absorption
-no secretions (relies on saliva)

Question 13

Omasum

Answer 13

-water reabsorption (30-60% of water entering)
-volatile fatty acid absorption (43-77% enter from rumen and are absorbed in omasum, 10% total)
>weak acids, but they can act as a buffer increasing pH, and decreasing digestion
-electrolyte absorption (Mg, K)

Question 14

Abomasum

Answer 14

-glandular “true”
-secretes HCl (pH 2.5-3.5)
-digestive enzymes
>pepsin from pepsinogen
>lysozyme (glycoside hydrolase; breaks open the peptidoglycan of gram-positive bacteria cell wall)
>Rennin (present prior to weaning)

Question 15

Microbial fermentation

Answer 15

-microbiome is critical for ruminant digestion
-fermentation requires controlled conditions for microbial growth

Question 16

Conditions needed for microbial fermentation

Answer 16

-38-38.5 C temp
-pH: saliva, absorption of VFAs
-Mixing: rumen motility
-Mechanical breakdown of particles through rumination

Question 17

Volatile Fatty Acids (VFAs)

Answer 17

-microbial fermentation of fiber (cellulose to glucose to VFAs)

Question 18

SCFA/VFA types

Answer 18

1.Acetate (2C)
2. Proprionate (3C)
3. Butyrate (4C)

Question 19

How are VFAs used?

Answer 19

-used by ruminants for energy
>Gluconeogenesis (Propionate to glucose)
»**need to make glucose because ruminants don’t get much glucose from their diets)
>lactating dairy cow produces ~5kg of glucose per day

Question 20

Types of ruminants

Answer 20

1.browsers
2.grazers
3.intermediates

Question 21

Browsers

Answer 21

-selectively eat high quality plant material (grain/seeds, fruit, leaves, bark, green stems)
>will have long jaw and tongue, thin lips
-higher concentrate diet (high in starch, rapidly fermentable)
-more frequent meals (faster fermentation= faster passage rate) which means they only need a small rumen capacity
-take less time chewer bolus
-Eg. Deer

Question 22

Grazers

Answer 22

-indiscriminately eat most plant material (mostly grass)
>short, round tongue and jaw with thick muzzle
-higher fiber diet (slower fermentability/digestibility)
-less frequent meals
-take more time chewing bolus
-eg. Cattle and sheep

Question 23

Intermediates

Answer 23

-Will eat anything (browser and grazer)
-eg.goats

Question 24

Intestinal anatomy of browser

Answer 24

-smaller rumen and omasum
-shorter SI, large cecum and colon (more hind gut fermentation)

Question 25

Intestinal anatomy of grazer

Answer 25

-larger more muscular omasum
-longer SI, shorter cecum and colon

Question 26

Consequence of Browser vs. grazer particles

Answer 26

-Browser: even particle size and mixture throughout rumen
-Grazer: stratification of different layers

Question 27

Stratification

Answer 27

-layers form based on particle density and size
-low density fiber raft (larger light particles float, middle is liquid, medium particles/where fermentation occurs, smaller particles and more dense at bottom
>rumination (mastication size decreases)
>fermentation (gas retention)

Question 28

Glucose for ruminants

Answer 28

-blood glucose spike is not occurring because they are not absorbing it
-glucose is what is being made in liver
-means they are less responsive to insulin