Gastrointestinal Physiology- Ruminent Flashcards
Ruminants
A diverse group of mammals that regurgitate and re-masticate their food
Suborders:
ruminantia- deer, elk, goat, cow, giraffe
Tylopoda- camel, llama
Fermentative Digestion
Occurs in specialized compartments localized before the stomach (forestomach in ruminants) or after stomach and small intestine (cecum and colon in horses)
Microbes in fermentative digestion
Bacteria, fungi, and protozoa
Enzymes for digestions are of microbial origin (not produced by host)
Regurgitation and re-mastication
provides more finely divided material and thereby a greater surface area for microbial digestion
nonglandular forestomachs
Rumen, reticulum, omasum
fermentative digestion
Terminal glandular
True stomach
Abomasum
Ruminent forestomachs
The forestomachs are lines with stratifies squamous epithelium
no villi or microvilli
Abomasum is mostly on the right side of the animal
Rumen development
The abomasum is the largest compartment of the newborns stomach
Enlargement of the forestomach occurs rapidly after birth but the rate depends on diet type (solid feeds and concentrate accelerate development) and contact with adult ruminants (inoculation of microorganisms)
Non-ruminant period: birth to 3 weeks
Transitional period: 3 to 8 weeks
Ruminent Stomach Protozoa
Most protozoa are ciliated and belong to the genus Isotricha or entodinium
Grouping of rumen protozoa according to morphology and size
Size: big, small, medium
Systematically: flagelates, ciliates
Ruminal environment
Substrate availability: food intake regulated by volume, structure, energy, palatability
Temperature: about 0.5-1 degree C above body temp
Fluids: drinking water and saliva
pH: 5.5-7 (acid synthesis and acid reabsorption, buffer substances coming from the saliva and rumen epithelium)
Ruminal ecosystem
Protozoa ingest large numbers of bacteria and hold bacterial numbers in check
Protozoa may also play a role in starch and protein digestion -> they prolong the digestion of these substances (ingest them and protect them from bacterial action)
Symbiosis
Waste products produced by only species serve as substrate for another
Generation and fate of VFA in the ruminant
Carbohydrates, proteins, and lipids
Digested by ruman microbes to VFA.
To propionate to the liver-glucose
To acetate butyrate to all tissues- energy
To acetate to adipose tissues- fatty acids
Fate of carbohydrates
The cell wall of plants has a large portion of carbohydrates whihc are important for stability and rigidity of the growing plant
Plant cell walls are important substrates for fermentative digestion (and significant nutrient source of many microorganism species)
Cellulose, hemicellulose, pectin- will be hydrolyzed by the enzyme cellulase. After hydrolysis, monosaccharides are not released from the polysaccharide. These monosaccharides are not available for absorption by the animal; further metabolized by the microbes
Lignin
Not a carbohydrate. Is essentially indigestible (although some fungi can digest lignin)
It increases with the age of a plant and ambiental temperature
Fate of carbs, proteins, and lipids
Essentially all dietary proteins and carbohydrates are subjected to fermentative digestion in the forestomachs
Products are glucose, other monosacch, and short chain polysacch. that are released into the fluid phase
These glucose and other sugars do not become available to the host animal; they are absorbed into the cell bodies of microbes
Within the microbial cell, glucose enters the glycolytic pathway
To produce 2 pyruvate from one glucose molecule (plus 2 NADH and 2 ATPs which is used by the microbes)
Fermentative digestion is an anaerobic and the products are volatile fatty acids (VFA aka short chain fatty acids SCFA)
Substrates and products of fermentative digestion
The primary VFAs are acetic acid (acetate), propionic acid (propionate), and butyric acid (butyrate).
Glucose –> pyruvate
Pyruvate to ACoA to acetate and butyrate OR Pyruvate to propionate OR Pyruvate (lack of O2) to lactate and to pripionate and acetate
Define Fermentative digestion
Enzymatic decomposition and utilization of foodstuffs by bacteria, fungi, and protozoa in forestomach of ruminants and cecum/colon in horses
What describes the rumen
Largest (by volume) compartment of ruminant forestomach
Seves as storach compartment to facilitate microbial fermentation of ingesta
Relevant ruminal microorganisms
Bacteria grouped according to food/ nutrients they ferment
Fungi assist with fermentative digestion
Protozoa are grouped according to their size and whether they have flagelates or cilates
Rumen environment
The time spent ruminating depends on type of feed ingested
Magic bus encounters glucose after eaten by cow
Glucose will leave the fluid phase and enter a microba when it will enter the glycolic pathway
Which do amino acids contribute to
Metabolized to VFA and ammonia
Synthesis of microbial protein
Protein and ruminant digestion
Proteins are particularly vulnerable to fermentation because they are made of carbon compounds that can be further reduced to provide energy for anaerobic microbes
Microbes do produce endopeptidases that form short-chain peptides as end products -> these peptides are then absorbed into the microbial cell bodies
Once in the microbial cell, peptides can be used to form microbial protein or can be further degraded for the production of energy
Protein metabolism by rumen microbes
Proteases on the microbe surfaces generate peptides
Intracellularly, peptides are hydrolyzed to amino acids
Amino acids contribute to: Synthesis of microbial protein and metabolized to VFA and ammonia
Amino acids are also synthesized intracellularly from NH3 and VFA
Deamination
Amino Acid to carbon skeleton and NH3
Normally the carbon structure of many animo acids can directly be used for VFA synthesis. An exception to this rule are the so called branch-chain amino acids (BCAAs)