Lecture 54- Ruminant Digestive Physiology I Flashcards
What is the gastric stomach?
Abomasum
What makes up the ruminant forestomachs? What type of cells?
Rumen, reticulum, omasum
Stratified squamous epithelium
No glands
Pillars and papillae
Describe the evolution of ruminants. What is the digestive strategy?
Ingest enormous quantities of forage in short time minimizing exposure in the open
Spend maximal time ruminating in the protection of trees and rocks
What is the ruminant GIT compartmentalized in:
Rumen, reticulum, omasum, abomasum
How is pre-gastric fermentation accomplished?
By microbes
Allows animals to more completely utilize products of fermentation
Pseudoruminats have no ______
Omasum
Where is the site of fermentation for ruminants?
Rumen
Where is the site of fermentation for non ruminants?
Cecum and large intestine
What are examples of ruminant species?
Cattle
Bison
Sheep
Antelope
Goats
Deer
Elk
How is food physically broken down?
*prehension-lips, tongues
*mastication during eating + rumination.
Rumination = regurgitation + remastication
*microbial fermentation (accomplished by bacteria, fungi, yeast, Protozoa)
What are the three major salivary glands?
Parotoid
Sublingual
Mandibular
What is the composition and function of saliva?
Composition: bicarbonate, urea, K, inorganic phosphate, Cl
**Buffering is the number 1 function, adding moisture and lipase
Which environmental conditions are needed to support fermentation?
Appropriate substrate
Temperature around 37
Osmolarity near 300 mOsm
Anaerobic conditions
Frequent mixing of ingesta
Particle size reduction
Indigestible material removal
Synchronized movement of fermented content to intestine
VFA must be buffered to maintain neutral pH
Where does 60-75% of digestion occur? Also the primary site of fermentation?
Rumen
What do amylolytic bacterial species consist of?
Starch and sugars
What do cellulolytic bacterial species consist of?
Cellulose, hemicellulose
What are the end products of fermentation?
Acetate, propionate, butyrate
*very important to remember: more acetate in high fiber and more propionate on high-grain**
What do papillae and extensive capillaries do in the rumen?
Increase surface area, absorb
*larger on high grain diets
What is the function of the reticulum?
Form bolus for regurgitation
Move particles to omasum
Move particles to rumen
How do materials from rumen pass into omasum?
Via the reticulo-omasum orfice
What does the omasum regulate?
Passage of digesta into lower tract
What is absorbed in the omasum?
Water and VFA
What do the gastric glands in the abomasum secrete?
HCl
Acidity kills microbes washing in from rumen—starts digestion
Major source of protein for animal essential AA -> digested and absorbed in SI
What does the abomasum secrete? And why?
Pepsinogen
Hydrolysis microbial and dietary protein
How many times do abomasal contractions occur?
2-3 per minute
Mixing, material exits to SI, and drive gas back into the rumen
What do forages contain?
Cellulose, hemicellulose, sugars, starch, protein, lignin
What do concentrates (grain) contain?
Starch, protein, sugar
What are the layers of the rumen?
-small high density on bottom
-liquid
-fibermat (larger, low density) -> scratch fiber
-then gas layer
What are examples of micro flora?
Bacteria, Protozoa, fungi
Primarily feeding the ______—then the cow.
Flora
What is the definition of fermentation?
Microorganism-mediated transformation from one nutrient compound to another
Which products undergo fermentation in the rumen?
Monosaccharide
Disaccharide
Starch
Cellulose
Other Sugars
Which carbohydrates are fermented in the rumen to VFA? and at what percent?
Acetate (60%)
Propionate (30%)
Butyrate (10%)
*acetate is higher with forage diets
*butyrate is higher with grain diets
What does gluconeogenesis use to make glucose?
Propionate
What does fat synthesis utilize?
Acetate
What do ruminants use for energy?
VFA
What is the blood glucose in most non-ruminants? Is this lower or higher than normal?
60 mg/dl
What is the pathway for sugars, starch, cellulose, and lignin to turn into VFA?
Sugar -> VFA
Starch -> Glucose -> VFA
Cellulose -> Glucose -> VFA
Lignin -> Undigested
What proteins fermented to?
Peptides
Amino acids
Ammonia
Branched-chain VFA
What do microbes use in synthesizing cell walls and the cytoplasmic reticulum?
Protein components and metabolites
Where are dead microflora digested?
Small intestine
What provides the highest quality protein possible?
Microbes
(TRUE/FALSE) If you feed low quality proteins or metabolites (urea) the cow absorbs lowest quality amino acids from small intestine.
FALSE
The cow absorbs the HIGHEST quality amino acids
What is ammonia produced in rumen from?
Protein fermation
What happens to the ammonia produced in the rumen?
Immediately utilized by microbes
Absorbed and converted to urea by the liver
What are the three fates of urea?
- Excreted by kidney
- Recycled to saliva
- Recycled to rumen
How do rumen primary contractions move?
Cranial to caudal
How do rumen secondary contractions move?
Caudal to cranial primarily to erucatate gas
What are reticular contractions associated with ?
Cud chewing
What are the four steps of rumination?
Regurgitation, reinsalviation, remastication, reswallowing
What is regurgitation initiated by?
Initiated by a reticular contraction AND relaxation of distal esophageal sphincter
When does rumination occur?
30-90 minutes after eating
Occurs when animal is resting
Ruminate up to 10 hours a day
What is the importance of rumination?
Rumination keeps food intake constant
Removes air and gas pockets from forage -> allows particles to sink
What is rumination is initiated by?
“Extra” contraction of reticulum that pushes ingesta into area of cardia
Which esophageal sphincter opens during rumination?
Distal esophageal sphincter
What is the process of rumination?
- Initiated by extra contraction of reticulum that pushes ingesta into area of cardia
- Distal esophageal sphincter open
- Inspirator excursion with glottis closed causing negative pressure in in trat Horacio esophagus
- Bolus of ingesta moves into esophagus
