carbohydrates and dietary fibre Flashcards
what is the nutritional role of carbohydrates?
providing immediate energy and storing energy in the form of glycogen and adipose.
what are the 2 primary energy nutrients
lipids and carbohydrates
what is absorbed from the gut lumen
monosaccharides
what carbohydrates do plants contain
cellulose
hemicellulose
lignin
what are the major sources of plant carbohydrates
seed endosperm
plant fibres
what does analysis of feed carbohydrate content provide
value for crude fibre
what do plant cell walls require to be digested
require microbial fermentation to yield VFAs
what are the cell contents
sugars and starches
how are plant cell contents digested in ruminants
hydrolysed to glucose by mammalian enzymes but fermented as FME to yield VFAs by ruminants
how are plant fibres digested in non-ruminants
have colonic bacteria which can digest some cellulose
how to increase FME
provide cereals
the effect of increasing FME by providing cereals in ruminants
increase rate of fermentation
synthesis of large quantities of VFAs reduces the PH of rumen contents so can cause rumen acidosis
what is the main source of energy in ruminants?
volatile fatty acids
process of absorption of VFAs
VFA absorbed across reticulorumen wall
remainder absorbed in omasum
transported to liver for processing
why are simple sugars absorbed directly by ruminants
they are quickly taken up by rumen microbes and converted to VFA
what is the normal rumen pH
6-7
what happens to the pH after a meal in ruminants and why
VFA lowers the pH and is buffered by saliva
what is formed in diets high in fibre in ruminants?
small amount of lactate formed and lots of ruminating hence saliva to buffer
what happens in diets high in starch in ruminants
quickly fermented, more VFA produced, faster and larger amounts of lactate
less fibre means rumination and less saliva to buffer pH
what is rumen a acidosis
low rumen pH
what happens in monogastrics following cereal meals
gastric acid synthesis increased and products of digestion further depress gastric pH
causes gastric perturbations including ulceration and colic
what is the effect on chewing and saliva production with diets high in fibre
increased time spent chewing which increases saliva production and neutralises acidic digesta
benefits of a high fibre diet
reduced gastric abomasal ulceration
reduced stereotypies
reduced dental overgrowth
reduced digestive perturbations
improved digestibility
the essential functions of fibre in cattle diets
stimulate cudding
form a rumen fibre mat which traps small particles for digestion and biofilm matrix
