rumen microbiology Flashcards
explain why herbivores requires microbes for digestion
- food consists mainly of beta linked polysaccharides (cellulose)
- cannot be broken down by mammalian digestive enzymes
- ruminants have evolved to use microbial fermentation of the food prior to normal digestion
- the bacteria produce products that can be directly used by the animal (volatile fatty acids)
- the bacteria also multiply on poor food to provide accessible form of proteins, nucleic acids, sugars and lipids. the bacteria themseves are digested by the ruminant
what are the benefits of microbial fermentation for the ruminant
- high quality protein from poor food material
- incorportate nitrogen from non-protein nitrogen sources. some of the rumen flora can incorporate nitrogen from urea into their protein synthesis
- incorporating hard to digest carbon into microbial proteins, nucleic acids, etc.
- essential amino acid synthesis thay cant be synthesised by the vertebrate themselves
- the mix of fermentinf microbes can synthesize amino acids
- vitamin B deficiency is rare in ruminants because their microbiota will produce all of them whereas mammals themselves can only synthesize 2 of the required B vitamins and require dietary sources of others
outline the fate of ingested complex polysaccarides in the ruminant
- ingestion of complex polysaccarides
- fermentation carried out by the microorganisms in the rumen resulting in production of:
- volatile fatty acids –> absorbed through the rumen wall
- gases (methane and CO2) –> erucated (belch)
- microbial cells and partially digested food –> passed onto the abomasum for further digestion here and in SI
bacterial respiration in the rumen is strictly ………
anaerobic
the 3 classes of the rumen microbiota are
- bacteria (most)
- protozoa (less but larger organisms)
- Fungi (fewest)
name and explain factors necessary for a stable microbial population in the rumen
- nutrients
- pH
- temperature
- Redox (O2 entering with food is rapidly absorbed by bacterial popultion)
explain how the pH is regulated within the rumen
- volatile fatty acid production lowers pH
- buffered by phosphate bicarbonate buffer from slaiva when reaches 5.5-6.5
- rapid absorption of the VFAs and ammonia keeps effects low
list the different metabolic classifications of microbes in the rumen
- major sugar utilizing
- major acid utilizing
- major proteolytic
- major ammonia producing
- major lipid utilizing
- cellulytic
- hemicellulytic
- pectinolytic
- amylolytic
- ureolytic
- methane producing
explain how oxygen levels are controlled in the rumen
- facultative anaerobes consume all oxygen to maintain their preferred anaerobic environment
- food entering reticulum is mixed with rumen content to allow bacteria to act to reduce the oxygen levels in the material prior to passing into the rumen
explain the basis of breakdown and cooperative metabolism in the rumen
discuss how methanogens are able to produce methane from organic material
empahsis on other bacteria breaking down parts before it reaches the methanogen (organism that produce methane as a metabolic by product in anaerobic metabolism
- homoacetogenic bacterial are strictly anaerobic and catalyse the formation of acetate from C1 units in their energy metabolism
- syntrophic bacteria/archaea live in syntrophic communities and take advantage of the metabolic abilities of their syntrophic partner to overcome energy barrier and break down compounds that they cannot digest themselves
- hydrolytic and fermentative bacteria are involved in hydrolytic reactions and breaking of polymer chains and fermentation chemical breakdown in situations where the electron trnasport chains is unusable and becomes the cells primary means of ATP
what are the disadvantages of rumen microbiota and how to overcome
- if a high quality feed is solely given the microflora might metabolise the easy to access compounds of the food before it reaches the animal
- important to balance with poor quality roughage
- rapid addition to some compounds can throw microbe food web out of balance
should you find active protozoa in rumen content
yes yes yes. markers for healthy rumen and visualised under microscope of rumen fluid. if mobile = healthy rumen microbiome
what is the purpose of fungi in the rumen
- colonise plant fragments in the rumen of ruminants on high fibre diets
- actively ferment cellulose and soluble sugars resulting in the generation of a mixture of products
- products include acetate, lactate, ethanol, formate, succinate, CO2 and H2
- help break up plant fibre
discuss how disruption to the rumen occurs and how to mitiagte effects
- sudden diet changes force microbiota to adjust but this takes time
- can take up to 2 weeks to re-establish a balance
- if suddenly give a lot of accessible carbohydrates, rapid production of VFAs can lead to acidosis
- if switching diet is necessary (dry cow to production) a transition is necessary to allow microbes to adjust to nutrient sources
