Ruminant 2 Flashcards
What is an example of true symbiosis?
Between the ruminant and its rumen microbes
How does symbiosis work in the ruminant?
-microbes of the rumen depend on the ruminant essential conditions
-ruminant provides habitat and microbes provide end products of fermentation
What are microbes essential for?
-Digestion and fermentation of fibrous feedstuffs that could not otherwise be used for nutrients.
What are some characteristics of the rumen?
-low oxygen environment
-very fluid: facilitates microbial interactions and enzymes with feed
-open and continuous ecosystem maintaining a stable microbial population
-carbohydrate rich
-a little is going to come out at a time
What gases are in the rumen?
-65% CO2, 7% N2, and 0.6% O2 in the rumen
What is the dry matter content in the rumen?
-varies from 6-18% depending on area in the rumen
Do fractalated or obliques like oxygen?
-Fractalated use oxygen
-Oblique don’t like oxygen
What type of environment favors lack of oxygen?
-lack of oxygen favors anaerobic microbes
What is the rumen support by?
-a constant supply of substrates (eating food) and a large holding capacity
-capacity aids in retention of complex diet components allowing degradation and fermentation
Since the rumen is carbohydrate rich what makes up most of the feed?
-cellulose and other polysaccharides
Are small or large particles retained until sufficient degradation has occurred?
-Large
What is the rate of passage (Kp)
-amount of liquid and particulates that flow out of the rumen per unit time
-typically expressed as a percentage 8%/h
What type of microbe diversity is in the rumen?
-Bacteria
-Protozoa
-Fungi
Characteristics of rumen bacteria
-digestion and fermentation of feed
-10^10 -10^11 / mL bacteria
-0.3-50 um
Characteristics of rumen protoza
-slow rate of pH decline
-majority are ciliated, but some flagellates
-contribute to fermentation
-predators of bacteria
What is rumen protozoa estimated to be comprised of?
-40% of microbial N
-60% of fermentation products
How does rumen protozoa contribute to fermentation?
-starch
-sugars
-pectin
-hemicellulose
Why are rumen protozoa predators of bacteria?
bacteria consumed for protein
Characteristics of rumen Fungi
-attachment site for bacteria
-10^2 - 10^4 / mL fungal zoospores
Classification of rumen bacteria by substrate:
cellulolytic, Hemicellulolytic and Pectinolytic, Amylolytic, Proteolytic, Ammonia producing, Lipolytic, Intermediate acid utilizers, and Simple sugar users
-cellulolytic = cellulose
-Hemicellulolytic and Pectinolytic = hemicellulose and pectin
-Amylolytic = starch
-Proteolytic = proteins
-Ammonia producing = amino acid deaminators
-Lipolytic = lipase producers
-Intermediate acid utilizers = lactate, succinate, formate
-Simple sugar users
Characteristics of anaerobic fungi
-attach to and found within plant fragments
-contribute to the degradation of cellulose and other polysaccharides
What makes up microbial interdependence?
-Intermediate cross feeding
-VFA requirements
-Interspecies hydrogen transfer
What is intermediate cross feeding?
-Intermediates being metabolites produced through cell processes
-sharing of intermediates between species
-end products of one become the substrate of another
Explain how B. succinogenes and S. ruminantium is an examples of intermediate cross feeding?
-Selenomonas ruminantium cannot use cellulose, but Bacteroides succinogenes does
-B. succinogenes produces succinate and S. ruminantium can use the produce succinate
Explain how lactate and Megashaera is an examples of intermediate cross feeding?
-lactate production, sometimes associated with starch feeding, can be used by Megashaera elsdenii to produce propionate
What can rumen bacteria not use?
-cellulose
What are VFA requirements in microbial interdependence?
-Sharing some VFA among non-cellulolytic and cellulolytic bacteria
-production of branched chain VFA like n-valeric or 2-methbutyric acids from deamination of branched chain amino acids by non-cellulolytic bacteria
-provides carbon skeletons
What does providing carbon skeletons do?
-for synthesis of amino acids
-also for synthesis of microbial fatty acids with branched or odd numbered chains
-found in the cell membranes of bacteria
What is interspecies hydrogen transfer relating to microbial interdependence?
-in the rumen there are H2 producing and H2 utilizing species
-much of the H2 is used to produce methane (CH4) from CO2
-Transfer of H2 to methane producers encourages more H2 production
-H2 producing pathways are associated with greater energy production
What does higher ATP yield by bacteria support?
-more bacterial growth
-more microbial protein production
What are the substrates of fermentation?
-Not lipids: hydrolyzed to free fatty acids and glycerol backbones, but not fermented in appreciable quantities
-some protein/amino acids utilization
-carbohydrates: structural and non-structural
Characteristics of carbohydrate substrates of fermentation
-several sugars are found in hemicellulose
-sugars: in feed or produced by polysaccharides hydrolysis
-starch
-pectin: early structural polysaccharides of developing plant cell walls
How does variable fermentation rates work?
-soluble CHO fermented first: sugars, some starch
-pectin next
-structural CHO, cellulose last
-easier to attack or hydrolyze substrates earlier and faster than harder to attack substrates
What does fermentation always follow?
Hydrolysis
What is pyruvate converted through a pathway?
VFA
What occurs in acetate production?
-pyruvate is first converted to acetyl-CoA
-Acetyl-CoA can then be converted to acetate propionate production
What are the three main pathways for propionate production?
-succinate pathway
-acrylate pathway
-propanediol pathway
What occurs on the butyrate production?
-butyrate is typically produced from butyryl-CoA which is derived from two molecules of acetyl-CoA
Examples of short chain fatty acids
-butyrate
-propionate
-acetate
What does 2 hexose produce?
-2 butyrate
-4 H2
-4 CO2
What does 3 hexose produce?
-4 propionate
-2 acetate
2 CO2
-2 H2O
What does Hexose + 2 H2O produce?
-2 acetate
-4 H2
-2 CO2
What is the molar ratio?
-acetate: propionate: butyrate
-70:20:10 (60:30:8)
What does hydrogen and carbon dioxide production do?
-Hydrogen inhibits higher energy yielding pathways
(hydrogen transfer)
What does hexose produce from methane?
-2 acetate
-CO2
-CH4
What does acetate from CO2 produce? (4 H2 +2 CO2)
-1 acetate
-2 H2O
What does hexose from acetate from CO2 produce?
3 acetate
