fibre ferm Flashcards
why cant monogastrics breakdown fibre
due to the beta glucan bonds
what is the reducing end in terms of polysaccharides ?
the end of the polysacc with an anomeric C1 not involved in a glycosidic bond.
which polysaccharide is a glucose polymer with an alpha 1-4 linkage
amylose
what is difference between amylose and amylopectin ?
amylopectin has alpha 1-4 linkages but also has branches formed by alpha 1-6 linkages.
how is glycogen rapidly available ?
has more alpha 1-6 linkages and highly branched structures permit rapid glucose release.
what type of linkage is cellulose ?
beta 1-4 linkage
2 hydrogens on opposite sides of linkage hence beta.
does more carbon FA’s in substrate increase or decrease energy
increase energy
butyrate highest carbons hence highest amount of energy.
why is high concentrate diet better than high forage diet
larger intake of feed less fibre and animal can harvest more energy from the diet.
what substrate does cellulose, starch and sugars go through to make butyrate, propionate and acetate.
pyruvate
does high pH result in more acetate or propionate being produced ?
acetate
does low pH result in more acetate or propionate being produced ?
propionate
what 3 factors affect fibre fermentation
- rumen pH
- rumen passage rate
- diet digestibility
what diets cause increase in VFA production
high starch diets
how does low pH impact fermentation ?
- microbial growth reduced
- energy once used for microbial production now diverted to maintain neutral pH.
what is the impact if passage rate is too high?
can reduce digestibility
which structures have rapid passage rate
simple structures eg sugars
which structures have slow passage rate ?
complex structures with high structural fibre content
what controls the flow of digesta out of rumen ?
reticulum
abomasum
why is optimum passage rate needed ?
- allow time for microbial fermentation
- absorbtion of VFA’s needs to occur
what is % of NDF that is essential in diets
30%
definition of degradability ?
how rapidly is feedstuff degraded in the rumen
definition of digestibility ?
how much of the nutrient consumed is digested and absorbed in the GI.
3 ways fibre of feedstuff is measured ?
- in Sacco
- in vitro
- NIR (infrared)
why does drop in rumen pH lead to drop in fat comp ?
leads to less acetate in mammary gland which is used to take up fat.
what can second rotation grass result in ?
drop in rumen pH and butterfat as it is highly fermentable.
what is the biggest challenge with forage only diets ?
trying to get enough rapidly digestible carbs to maintain rumen function.
