Lecture 10 - Ruminant Anatomy and Digestion Flashcards
Phylum, class, subclass, order and suborders of ruminants
Cordata, mammals, ungulata (hooved), ariodactyla (even-toed)
Sub orders:
Tylopoda (pseudo-ruminants e.g. camel, llama)
Ruminantia (true ruminants e.g. cattle, deer)
Components of ruminant anatomy
Rumen, reticulum, omasum, abomasum
Motility in the reticulo-rumen
Mixing, eructation, rumination
On what side would you see the omasum and abomasum
The right side
Instead of villi, the rumen wall has…
Papillae
Characteristics of the rumen papillae
- 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
Role of papillae in rumen
Increase surface area for absorption of SCFA from fermentation
Main function of the rumen
Large compartment for microbial fermentation
Characteristics of the rumen wall
Stratified squamous epithelium (partially keratinized)
Papillae
Sensory receptors
Sensory receptors of the rumen wall
Tension receptors: excited by passive distention
Epithelial receptors: excited by physical and chemical stimuli
Rumen environment
Moist and warm
pH 5.5 - 7.1
Gas production
Regular addition of new digesta
Rumen absorbs..
fermentation end products
- SCFA = acetate, propionate, butyrate and ammonia
Characteristic of the reticulum wall
Stratified squamous epithelium
Honeycomb appearance
Partially separated from cranial sac of rumen
The rumen and reticulum..
Are anatomically different, but operate as a combined functional unit
Rumen and reticulum contraction facilitates
Regurgitation for rumination
Mixing digesta in the reticulo-rumen
Passage of digesta to the omasum
What is the reticular groove
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
Characteristic of the omasum, its role
Stratified squamous epithelium, consists of many leaves (laminae)
Absorption of water and VFA
Role of the abomasum. Walls?
True stomach secreting acid (HCl) and enzymes
Mucosal epithelial cells
**Know pics of different compartments
ok
At 3 days old, the forestomach is made up mostly of… At 3 months old/ adult…
Abomasum at 3 days
Rumen as adult
Sequence of motility of reticulo-rumen (mixing)
- Double contraction in the reticulum
- Anterior dorsal sac of rumen
- Caudal region of rumen
- Main ventral rumen
- Caudoventral sac
Slide 17
What does rumen contraction do in terms of VFA
Enhances absorption, mix digesta so VFA are redistributed evenly
Where is the gas layer in the rumen? Intense fermentation occurs where? Moderate fermentation occurs where/aka?
Gas layer at top
Intense fermentation in middle region (fiber mat and intermediate zone)
Moderate fermentation at bottom aka liquid zone
Sequence of steps for motility of reticulo-rumen (eructation)
- Starts in caudoventral sac
2-4. Sweeps across the dorsum to reach vicinity of the cardia - Completed with contraction of the main ventral rumen
Slide 21
What is eructation
Gas distends dorsal rumen, gas bubble pressed against cardia and is forcibly ejected into esophagus by contraction of main ventral rumen
How does motility of reticulo-rumen work during rumination
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
Why do we need to re-masticate during rumination
Digesta too large to enter omasum
Daily time/periods spent ruminating
14 periods over 24 h
Cattle on hay = 8 h
Cattle on concentrates = 2.5 h
How does particle size of alfalfa affect chewing time
Corse alfalfa has higher eating time and ruminating time than fine alfalfa
Slide 29
Metabolism for VFA production
Fermentability of starch, fiber, sugar ranked
Sugar > starch > fiber (slowest)
What happens when there’s excess ruminal fermentation
Greater fermentation acid production (VFA, lactate)
What determines ruminal pH
Balance between VFA production and buffering (saliva secretion contains buffer stimulated by rumination) capacity of rumen
Slide 32**
Important
Most SCFA are produced by… Which SCFA?
Microbes produce acetate
How does high starch vs high fiber diet affect VFA production
High starch diet means more acetate production, more propionate production
How do protonated vs deprotonated acetate cross the rumen epithelium
Deprotonated need facilitated diffusion exchange with bicarbonate
Protonated can do simple diffusion
As rumen pH decreases what happens to propionate, acetate and lactate production
Acetate and propionate start to decrease around pH 5
Lactate begins to increase
Role of acetate
Energy source in most tissues
Substrate for f.a. synthesis in adipose tissue/mammary gland
Not used for glucose synthesis
Role of propionate
Primarily taken up by liver to produce glucose
Role of butyrate
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
Directly after eating, what happens to rumen pH and total VFA?
Rumen pH drops, total VFA increases
Rank good quality hay, concentrate mix/grain and poor quality hay based on digestibility
(most digestible) concentrate mix/grain <- good quality hay <- poor quality hay
