Lecture 10 - Ruminant Anatomy and Digestion

Question 1

Phylum, class, subclass, order and suborders of ruminants

Answer 1

Cordata, mammals, ungulata (hooved), ariodactyla (even-toed)
Sub orders:
Tylopoda (pseudo-ruminants e.g. camel, llama)
Ruminantia (true ruminants e.g. cattle, deer)

Question 2

Components of ruminant anatomy

Answer 2

Rumen, reticulum, omasum, abomasum

Question 3

Motility in the reticulo-rumen

Answer 3

Mixing, eructation, rumination

Question 4

On what side would you see the omasum and abomasum

Answer 4

The right side

Question 5

Instead of villi, the rumen wall has…

Answer 5

Papillae

Question 6

Characteristics of the rumen papillae

Answer 6

• have highly vascularized connective tissue
• lack smooth muscle, therefore do not move
• cells in contact with contents are keratinized/dead
• cell renewal takes place in stratum basale

Question 7

Role of papillae in rumen

Answer 7

Increase surface area for absorption of SCFA from fermentation

Question 8

Main function of the rumen

Answer 8

Large compartment for microbial fermentation

Question 9

Characteristics of the rumen wall

Answer 9

Stratified squamous epithelium (partially keratinized)
Papillae
Sensory receptors

Question 10

Sensory receptors of the rumen wall

Answer 10

Tension receptors: excited by passive distention
Epithelial receptors: excited by physical and chemical stimuli

Question 11

Rumen environment

Answer 11

Moist and warm
pH 5.5 - 7.1
Gas production
Regular addition of new digesta

Question 12

Rumen absorbs..

Answer 12

fermentation end products
- SCFA = acetate, propionate, butyrate and ammonia

Question 13

Characteristic of the reticulum wall

Answer 13

Stratified squamous epithelium
Honeycomb appearance
Partially separated from cranial sac of rumen

Question 14

The rumen and reticulum..

Answer 14

Are anatomically different, but operate as a combined functional unit

Question 15

Rumen and reticulum contraction facilitates

Answer 15

Regurgitation for rumination
Mixing digesta in the reticulo-rumen
Passage of digesta to the omasum

Question 16

What is the reticular groove

Answer 16

Conduit for milk from the cardiac opening to the reticulo-omasal opening, then through the omasum to abomasum (no need to ferment milk, it is highly digestible)
Closure of groove is a reflex initiated when receptors in the mouth/pharynx are stimulated

Question 17

Characteristic of the omasum, its role

Answer 17

Stratified squamous epithelium, consists of many leaves (laminae)
Absorption of water and VFA

Question 18

Role of the abomasum. Walls?

Answer 18

True stomach secreting acid (HCl) and enzymes
Mucosal epithelial cells

Question 19

**Know pics of different compartments

Answer 19

ok

Question 20

At 3 days old, the forestomach is made up mostly of… At 3 months old/ adult…

Answer 20

Abomasum at 3 days
Rumen as adult

Question 21

Sequence of motility of reticulo-rumen (mixing)

Answer 21

1. Double contraction in the reticulum
2. Anterior dorsal sac of rumen
3. Caudal region of rumen
4. Main ventral rumen
5. Caudoventral sac
   Slide 17

Question 22

What does rumen contraction do in terms of VFA

Answer 22

Enhances absorption, mix digesta so VFA are redistributed evenly

Question 23

Where is the gas layer in the rumen? Intense fermentation occurs where? Moderate fermentation occurs where/aka?

Answer 23

Gas layer at top
Intense fermentation in middle region (fiber mat and intermediate zone)
Moderate fermentation at bottom aka liquid zone

Question 24

Sequence of steps for motility of reticulo-rumen (eructation)

Answer 24

1. Starts in caudoventral sac
   2-4. Sweeps across the dorsum to reach vicinity of the cardia
2. Completed with contraction of the main ventral rumen
   Slide 21

Question 25

What is eructation

Answer 25

Gas distends dorsal rumen, gas bubble pressed against cardia and is forcibly ejected into esophagus by contraction of main ventral rumen

Question 26

How does motility of reticulo-rumen work during rumination

Answer 26

Additional reticular contraction before biphasic contraction (triphasic) Soft palate is elevated, closes nasal passage Inspiratory muscles expand thorax Reverse peristalsis lifts bolus into buccal cavity Re-mastication and re-insalivation Re-swallowing

Question 27

Why do we need to re-masticate during rumination

Answer 27

Digesta too large to enter omasum

Question 28

Daily time/periods spent ruminating

Answer 28

14 periods over 24 h Cattle on hay = 8 h Cattle on concentrates = 2.5 h

Question 29

How does particle size of alfalfa affect chewing time

Answer 29

Corse alfalfa has higher eating time and ruminating time than fine alfalfa

Question 30

Slide 29

Answer 30

Metabolism for VFA production

Question 31

Fermentability of starch, fiber, sugar ranked

Answer 31

Sugar > starch > fiber (slowest)

Question 32

What happens when there's excess ruminal fermentation

Answer 32

Greater fermentation acid production (VFA, lactate)

Question 33

What determines ruminal pH

Answer 33

Balance between VFA production and buffering (saliva secretion contains buffer stimulated by rumination) capacity of rumen

Question 34

Slide 32**

Answer 34

Important

Question 35

Most SCFA are produced by... Which SCFA?

Answer 35

Microbes produce acetate

Question 36

How does high starch vs high fiber diet affect VFA production

Answer 36

High starch diet means more acetate production, more propionate production

Question 37

How do protonated vs deprotonated acetate cross the rumen epithelium

Answer 37

Deprotonated need facilitated diffusion exchange with bicarbonate Protonated can do simple diffusion

Question 38

As rumen pH decreases what happens to propionate, acetate and lactate production

Answer 38

Acetate and propionate start to decrease around pH 5 Lactate begins to increase

Question 39

Role of acetate

Answer 39

Energy source in most tissues Substrate for f.a. synthesis in adipose tissue/mammary gland Not used for glucose synthesis

Question 40

Role of propionate

Answer 40

Primarily taken up by liver to produce glucose

Question 41

Role of butyrate

Answer 41

Utilized by ruminal wall as energy source, and ketones produced from butyrate in ruminal wall serve as E source and substrate for f.a. synthesis

Question 42

Directly after eating, what happens to rumen pH and total VFA?

Answer 42

Rumen pH drops, total VFA increases

Question 43

Rank good quality hay, concentrate mix/grain and poor quality hay based on digestibility

Answer 43

(most digestible) concentrate mix/grain <- good quality hay <- poor quality hay