Rumen physiology Flashcards
what does ruminare mean
to chew over again (latin)
why is the cud not acidic
comes from the first and second compartments that have a more neutral pH
true v. pseudoruminants
- true: 4 compartment stomach
- pseudo: 3 compartments (no omasum)
2 theories of ruminant evolution
- “eat and run”
- detoxification of plant substances
what % of digestion do ruminant microbes account for
70%
does rumen wall secrete enzymes or not?
no
functions of rumen (4)
- storage
- soaking
- physical mixing and breakdown
- fermentation
what does pregastric fermentation consist of (3)
- bacterial synthesis of water soluble vitamins and vitamin k
- bacterial synthesis of amino acids and protein
- breakdown of fibrous feeds
what is wall of reticulum lined with? does it secrete enzymes?
- lined with mucous membrane
- no enzymes
function of reticulum
moving ingested feed into rumen or omasum
what is omasum filled with
muscular laminae
function of omasum
reduce particle size of ingesta
is abomasum glandular or nonglandular
glandular
where does reticular (esophageal) groove extend from
cardia to omasum
steps in rumination (4)
- regurgitation
- remastication
- resalivation
- reswallowing
eructation
elimination of CO2 and CH4 (endproducts of fermentation)
advantages of pregastric fermentation (6)
- utilization of cellulose as energy source
- conversion of NPN to microbial protein
- N recycling
- microbial detox of plant compounds
- reduction of B-vitamin req
- absorption of microbial end products
disadvantages of pregastric fermentation (3)
- can lose energy from fermentation as heat, methane
- amino acid balance may not be improved
- many drugs can’t be fed orally
is the rumen oxidating or reducing
reducing
what is rumen rich in and deficient in
- rich in organic matter
- deficient in readily metabolizable compounds
range of DM % of rumen contents
7-15%
what % of body weight does rumen comprise of
7-15%
what % of total stomach volume is rumen
80-85%
does rumen secrete digestive juices
no
how are end products/wastes from fermentation removed
diffusion across rumen wall
2 mechanisms for keeping rumen pH near neutrality
- continuous influx of saliva (phosphate-bicarb buffer, some urea/mucous, no enzymes)
- diffusion across rumen wall (more VFA diffuse into blood than omasum)
rumen temperature
34-40 C, may be as high as 41 in active fermentation
rumen gases
- CO2 (65%)
- CH4 (27%)
- H2 (0,2% –> used to reduce CO2 to CH4)
- N (7%)
- trace H2S, O2
rumen facultative anaerobic bacteria
O2 scavenging activity to maintain anaerobic conditions
how does urea enter rumen
feed supplement, saliva, diffusion across rumen wall –> source of NH3
what bacteria have higher urease activity
adherent bacteria (also scavenge O2)
ecological niches
- liquid phase: free-living microbial groups in fluid (25%)
- solid phase: microbial groups w/ food particles (70%)
- rumen epithelium: microbial groups attach to animal cells (5%)
growth of microbes adhered to feed particles
- net growth rate less than liquid dilution rate
- growth rate related to solids turnover
growth of microbes adhered to rumen wall
relatively slow net growth rate
rumen microbial population (5)
- bacteria
- archae
- ciliated protozoa
- flagellated protozoa
- fungi
- bacteriophage
functions of bacteria (9)
- cellulolytic
- amylolytic
- hemicellulolytic
- pectinolytic
- ureolytic
- proteolytic
- methanogenic
- glucolytic
- lipid utilizers
what does rumen hydrolyze fatty acids (triglycerides) into
free fatty acids, glycerol
biohydrogenation
- follows hydrolysis or lipolysis
- caused by rumen microbes
- addition of H to fatty acids with double bonds
- converts all double bonds –> saturated FA
synthesis of lipids
odd-carbon chain and branched-chain FA
how does most fat enter SI
as non-esterified FA that are highly saturated
effects of defaunation (removing protozoa)
- VFA concentration:
- acetate/butyrate concentration:
- propionate concentration:
- ammonia concentration:
- lactic acid concentration:
- bacterial numbers:
- protein degradation:
- cellulose digestion:
- VFA concentration: dec
- acetate/butyrate concentration: dec
- propionate concentration: inc
- ammonia concentration: dec
- lactic acid concentration: inc
- bacterial numbers: inc
- protein degradation: dec
- cellulose digestion: dec
role of fungi
- synthesize enzymes
- more effective in cellulose digestion
- enterases (not in bacteria) for hemicellulose/ligin
- penetrate plant cuticle
- pectin degradation
- grain digestion
- choline synthesis
relationship between ruminal bacteria and fungi
inverse relationship (bacteria produce bacteriocin-like substance to inhibit fungi)
