Voluntary Feed Intake Flashcards
If thinking about rumen fill as a way to increase feed intake when and what would you want to fill the rumen with?
Stretch with poor quality forage, PRIOR to lactation to maximise feed intake during lactation.
What is the most potent VFA for causing feeding depression?
Acetate - this is closely followed by propionate.
n.b. Butyrate absorbed slower and can result in rumen stasis, it is a result of poorly fermented feeds.
What factors, other than chemostatic and distension feedback can decreased VFI?
Higher body fat
Pregnancy
Inert fill (fibre)
Dietary Neutral Detergent Fibre
How does water affect feed intake?
Water drunk with food has little effect
Water in plant material can have a significant effect in reducing intake.
What is NSP and how does it affect VFI?
Soluble fibre/ non-starch polysaccharides. It slows feed passage through the intestine.
n.b. can reduce this effect by reducing fibre length
What is a rough estimate of DM intake of a cow?
20-25kg/Day
What is the effect of pregnancy on feed intake?
How can this be dealt with?
It will drop and the rate of passage of things through the gut will increase therefore feed is not fermented to the same degree. (n.b. this is inert fill)
Can add more digestible food!
What is a good external indicator of rumen acidosis? this may be seen around the farm…
Particulate matter in the dung as acidosis disturbes particle flow rate
What is the glucostatic hypothesis?
Is this theory applicable to farm animals?
The glucoreceptors in the CNS (hypothalamus) are sensitive to the rate at which glucose is utilised. Therefore they can stimulate hunger if this is at a high rate.
Applicable to pigs but not poultry or ruminants (as glucose mainly from hepatic/aa sources)
What is hepatic oxidation theory (HOT) and how does it relate to hunger?
ATP levels in liver determine vagal stimulation therefore low levels of ATP production stimulate hunger.
How does thermostatic theory apply to ruminants?
Not a good estimation for feed intake as the rumen is an exothermic organ in itself.
What is the hormone of the lipostatic theory of energy balance?
What happens to levels of this hormone in dairy cows?
Leptin. - increased leptin the reduced feed intake (although this is not a clear cut theory)
It is very low as there is often a NEB in these animals as they put a lot of energy into mammary maintainance
For animals other than dairy cows what is a good estimate of DMI?
2xBW
What is NDF and why is it useful?
It is from plant cell walls. It is most useful for predicting how much forage a cow can consume.
What is ADF used for?
It is used to predict the energy content of forages as it is inversely related to digestibility. (probably as it is the stuff that makes up cell walls e.g. lignin which is harder to digest)
