Lesson 74 - Microflora of Ruminants

What is the most abundant microorganism of the rumen?

bacteria

What do CAZ-enzymes degrade?

lignocellulose

What bacteria are cellulolytic?

Ruminococcus, Fibrobacter, Butyrivibrio

What bacteria are Amylolytic?

Streptococcus, Prevotella, Ruminobacter

What are protein-degrading bacteria?

Ruminobacter, Butyrvibrio

What are fat-degrading bacteria?

Anaerovibrio lipolytica

What are lactic acid producing bacteria?

Bifidobacterium, lactobacillus, Streptococcus

What are lactic acid utilizing bacteria?

Selenomonas and Megaspheara

What are the main type of protozoa present?

ciliates

What is the most dominant genus of protozoa?

Entodinium

What is the role of protozoa?

feed degradation by breaking down plant fibers

What are protoza symbiotic with?

archaea which contributes to methane production

What is the dominant arcaea present?

Mehanobrevibacter

What do methanogens (Archaea) play a key role in?

fermentation process; using hydrogen to produce methane

What are the type of methanogens?

free-living, epithelial surface, protozoa-associated

What type of fungi are present?

anaerobic

What is the dominant phylym of fungi?

Neocallimastigomycota

What is the function of fungi?

degrade recalcitrant plant material and synthesize high levels of cellulases, hemicellulases, xylanases

What types of viruses are present?

bacteriophages an archaeaphages

What is the most dominant virus?

Siphoviridae

What is the function of viruses?

microbial lysis

What happens between viruses and other microbes?

genetic exchange

What is being produced in the rumen?

volatile fatty acids, methane, microbial proteins, vitamin

What is being degraded in the rumen?

fiber

What is being disposed of in the rumen?

hydrogen

What is being converted in the rumen?

nutrients

What can ruminants not produce?

cellulolytic and hemicellulolytic enzymes

What do microbiota break down that the rumen can't itself?

cellulose, hemicellulose, lignin

What does degradation of cellulose, hemicellulose, lignin release?

energy stored in the plant cell walls

What microbe helps degrade lignocellulose?

bacteria

What microbe helps degrade plant cell tissue and plant cell walls?

fungi

What happens during fermentation of hexose and pentose sugars?

Acetyl-CoA is produced

What does fermentation of Acetyl-CoA produce?

acetate, propionate, butyrate

How does the host absorb volatile fatty acids?

monocarboxylate transporters

What do volatile fatty acids generate?

ATP for synthesis of microbial cellular protein

What is the most abundant volatile fatty acid?

acetate

What is a soluble CH?

starch

What is structural CH?

cellulose, hemicellulose, pectin

What breaks down starch?

amylolytic microbes

What is the major energy source for ruminants?

volatile fatty acids

What does starch, cellulose, hemicellulose, pectin get converted into?

fructose (1-6-biphosphate)

What does fructose get converted into after glycolysis?

pyruvate

What is produced from glycolysis of fructose?

pyruvate, 2 ATP and NADH2

What does pyruvate get converted into?

propionate, butyrate, lactate, acetate

What can lactate be converted into?

propioate and acetate

What is produced when converting pyruvate into propionate and butyrate?

NADH2 to NAD+

What is produced when converting pyruvate into acetate?

2 CO2 and ATP

What does the carbon dioxide from making acetate turn into?

CH4

What is going to happen to acetate?

lipogenic so travel to liver and make fat

What is gluconeogenic?

propionate

What is ketogenic?

butyrate

How do unionized fatty acids get absorbed?

through the membranes since lipophilic with low rumen pH

How do ionized fatty acids get absorbed?

bicarbonate/VFA exchanger

What happens to pH as more fatty acids are produced?

decreased pH

Which carbohydrates are fermented faster?

soluble carbohydrates

What does the microbiota convert indigestible forages, food by-products, and non-protein nitrogen into?

microbial protein which is a vital source of amino acids for the host animals which helps make high-grade meat and dairy products for consumption

What are dietary proteins fermented into?

ammonia (NH3) and VFAs

What do microbes need for their own growth?

VFA, nitrogen source, ATP

What is the bottleneck for microbe nutrients for themselves?

nitrogen source

What are the natural sources for nitrogen for microbial protein synthesis?

ammonia and urea

What is urea a waste product from?

protein catabolism

Why is urea formed?

detoxify ammonia from catabolism of endogenous amino acids and ammonia absorption from the rumen and large intestines

What happens if ammonia concentration is too high in rumen?

urea is excreted via the kidneys

What happens if the ruminal ammonia concentration is too low?

urea is secreted directly or via saliva into the rumen for bacterial growth; ammino nitrogen recycling

How do ruminants meet their protein requirements?

digesting microbes that are flushed into the omasum, abomasum, or small intestine

What is the primary means of utilizing hydrogen as an electron acceptor?

methanogens

What are the ways of disoposing of hydrogen?

methanogenic archaea consume hydrogen, reduced CO2 to methane, methanogens using hydrogen, disposed of by nitrate and sulfate reduction by bacteria

What kind of genes undergo horizontal gene transfer?

degradation of plant cell walls and adaptation to specific rumen conditions

What are factors that affect the rumen microbiome?

diet, feed additives, host genetics, early-life interventions

What are some feed additives?

probiotics, prebiotics, phytobiotics

What are early-life interventions?

weaning and supplements

What are the types of diets?

forage based and starch rich (concentrate diets)

What is important about forage based diets?

neutral detergent fiber, increased concentrations of protozoa and methanogens, less acidic, wider range of substrates

What is important about starch-rich diets?

decreases the bacterial richness and diversity, decreases rumen pH due to increased production of short volatile fatty acids, lead to ruminal acidosis

What is a key driver for the rumen virome?

dietary energy

What are prebiotics?

non-digestible dietary substances that stimulate the activity of beneficial microbes in the gut; usually oligosaccarides

What are phytobiotics?

tannins, flavonoids, essential oils; plant secondary metabolites with anti-inflammatory, antioxidant, and antimicrobial properties

What is the importance of phytobiotics?

reduce methane emissions, antimicrobials, improve animal productivity

How do the young get microbes?

vertical transmission through the placenta, umbilical cord, amniotic fluid

What supplements can you give the dam to improve microbiome during gestation?

mineral supplementation

What supplement can you give calves to enrich microbes?

methionine enriched microbes and metabolites

What are causes of rumen dysbiosis?

dietary changes, stressful events, treatment especially antibiotics, change of environment

What are consequences of rumen dysbiosis?

reduced feed efficiency, nutrient imbalances, increased risk of metabolic disorders, increased methane production, compromised immune response

How does rumen dysbiosis cause reduced feed efficiency?

disrupts microbe balance and lowers feed conversion efficacy meaning animals need more feed to produce same amount of milk or meat

How does rumen dysbiosis cause nutrient imbalances?

disruptions in microbiome impair the conversion of NPN into microbial protein, reducing amino acids available for the host

What metabolic disorders can result from rumen dysbiosis?

ruminal acidosis and ketosis

What does ruminal acidosis result from?

rapid increase in the consumption of starch-rich concentrates

What bacteria like acidic environment?

Streptococcus bovis and Lactobacillus species

Why does ketosis result from rumen dysbiosis?

animals energy demands exceed energy intake because of the disruption of microbiome

How does rumen dysbiosis result in increased methane production?

imbalance methanogen microbial populations

What is the dominant arcaea present?

Mehanobrevibacter