Animal nutrition - feed intake Flashcards
The term „intake“ expresses
the daily consumption amount of natural feed, feed dry
matter, or any nutritive factor (ME, MP, etc.)
Consideration of ration intake is the first step in
ration formulation
In feeding, dry matter (DM) intake is
the most important, because this is limited by the
capacity of the digestive tract.
DM intake =
feed amount – feed moisture
DM intake is most commonly calculated in
kg per 100 kg live weight,
or in % of the animal’s body weight
in farm animals, DM intake is about
2…5% of body weight,
in poultry slightly higher
in dairy cows, DM intake is
in dairy cows 2.0…(3.0…3.5)…4.0 % of body weight
▪ if the ration contains only silage, then 2.2…2.5 %
▪ depends on the ratio of roughages to concentrates in the ration, i.e. the fibre content
The lower the animal’s body weight is, the greater the
relative feed intake.
Today, it is considered that high production cows eat more, because a lot of nutrients are excreted with the milk, and these nutrients must be received in the ration.
Thus, feed intake determines
the potential animal production!
DM intake control is what type of process?
DM intake control is a neuro-hormonal process
The food Intake controlling centre is located in
the hypothalamus
According to a simplified scheme there are what two active centres involved in feed intake control
first: feeding centre, which motivates the animal to eat until an intake inhibiting signal is received from the other centre
second: satiety centre, which receives signals from the body about the intake, and if necessary inhibits the activity of the feeding centre
How do Peptide hormones relate to feed intake control?
Peptide hormones have a central role in feed
intake control.
They provide the signals to the hypothalamus about the animal’s energy status.
Most important peptide hormones are (4)
insulin
leptin (from adipose tissue)
ghrelin and gastrin (both synthesized in the GI tract)
▪ and others, like peptide YY, oxyntomodulin,
cholecystokinin, glucagon-like peptide 1 etc.
What feeding related peptide hormones do not affect the hypothalamic satiety centre?
The exceptions are ghrelin (the so-called
“hunger-signalling hormone”, and thus affects
the feeding centre)
and gastrin (reduces the sensitivity of rumen tension receptors).
Productive animals (dairy cows) intakes are
mainly determined by what 2 types of factors?
physical factors (these include chemical)
metabolic factors
physical (and chemical) factors that detremine intake control are
related to total digestive tract capacity (rumen fill)
In practice, in dairy cows feed intake is limited at the beginning of lactation by the metabolic load, and at the second half of the lactation by the physical capacity of the rumen.
metabolic factors that detremine intake control are
related to the animal’s ability to use feed energy
In practice, in dairy cows feed intake is limited
at the beginning of lactation by the metabolic
load, and at the second half of the lactation by
the physical capacity of the rumen.
at the same growth phase grasses, compared to legumes, contain less
lignin, and therefore their digestibility is
higher which makes their intake / passage rate higher too
at the same digestibility legumes, compared to grasses, contain less
cell wall and more intracellular substances,
and therefore their intake is ca 20% higher
intense ammonia production in the rumen reduces
feed intake and in extreme cases can stop the
contractions of the forestomachs
sugar and starch sources degrade in the rumen faster compared to
fibre sources (roughage to concentrate
ratio)
passage rate of faster degradable feeds is higher, and therefore their intake is
higher
acidic environment reduces rumen fibre digestion resulting in intake being…?
intake is lower
rumen fibre digestion is associated with what type of bacteria?
rumen fibre digestion is associated with cellulolytic bacteria
Digestibility of cellulose depends on
ruminal pH
Digestibility of cellulose can be 98% at a pH of 6.4
…
87% at 6.1
28% at 5.7
0% at 5.6
At temperatures above 25°C, feed intake decreases by ?% for every 5°C
At temperatures above 25°C, feed intake decreases by 10% for every 5°C
to avoid dairy cow overheating farmers can use
ventilators or water showers
The maximum feed intake of cows is at what temperature?
The maximum feed intake of cows is at 7-10°C
at the beginning of lactation the use of glucose in peripheral tissues…?
decreases, and majority amount of
synthesised glucose is transported into the udder to support milk synthesis
thus, insulin resistance is a normal state for high yielding dairy cows
what type of effect growth hormone have
when insulin content decreases?
antagonistic effect of growth hormone -> it increases, while insulin content decreases
the main hormone in the blood which
regulates the metabolism of carbohydrates (glucose)
insulin
In monogastrics, what 2 hormones increase in the blood after feeding
glucose with insulin and leptin, increase in the blood, and due to this the animal stops eating
In ruminants, at the beginning of lactation the glucose and insulin levels in blood are
low -> this stimulates gluconeogenesis in the liver and activates the enzyme lipase in adipose tissue
In ruminants, at the beginning of lactation, tissue insulin resistance is high and due to this the increase of
glucose and/or insulin does not reduce the use of body fats
use of body fats increases blood Non-esterified (“free” or unsaturated) fatty acids content and supresses intake
In ruminants, as lactation progresses, the insulin content in blood, and tissue insulin sensitivity starts to
increase, and due to this feed intake
increases
The liver’s role in feed intake regulation is referred to as the?
hepatic oxidation theory
The liver, as „hardware“, is connected to the intake centre in the brain via the hepatic vagus nerve.
Feed intake is controlled via the stimulation
intensity of the vagus nerve.
Feed intake is controlled via the stimulation
intensity of the vagus nerve. this is determined by
the amount of organic matter oxidised in the liver, and from this, ATP is produced
reduced stimulation of the hepatic vagus nerve is associated with
a perception of satiety
(more organic matter -> more ATP -> do not eat)
increased stimulation of the hepatic vagus nerve is associated with
hunger
(less organic matter -> less ATP -> eat)
After calving dairy cow feed intakes are usually
influenced by
metabolic load
In the liver, two competing pathways work in parallel and in both the key compound is
oxalacetate
In the liver two competing pathways work in parallel. What are they
- Synthesis of glucose from propionate, AAs, and glycerol originating from adipose tissue
- Oxidation of body FAs and VFAs into ATP
In the liver two competing pathways work in parallel, and in both the key compound is oxalacetate. Which pathway is preferred?
- Oxidation of body FAs and VFAs into ATP
(1st being: Synthesis of glucose from propionate, AAs, and glycerol originates from adipose tissue)
The second is preferred, and therefore the
liver can convert propionate obtained from
concentrates into ATP, which reduces intakes.
Name 3 types of ruminal receptors that influence feed intake.
ToR – temperature receptors
TR – tension receptors
CR – chemo receptors
Name 5 factors affecting feed intake in ruminants that aren’t physicochemical or metabolic factors.
The animal itself per se (size and genotype)
Composition of the feed ration
Palatability of feeds
Milk production
Stage of lactation
What attributes of feed composition affect feed intake (5)
silage quality,
digestibility (amount and composition of
cell wall substances),
ration DM (ca 45%),
level of feeding,
roughage to concentrate ratio
Cows eat ?% more wilted silage than unwilted
silage.
Cows eat 16% more wilted silage than unwilted
silage.
It is believed, that due to dehydration, the
volume of grass plant cells decreases, and
therefore they can fit more easily into the rumen.
The fine particles of the wilted silage pass
through the rumen faster than unwilted silage
particles.
Cows eat most silage when its dry matter content is ?%.
Cows eat most silage when its dry matter content is 41.7%.
Silage pH has a small impact on
feed intake
NH3 is negatively correlated with
intake
it is believed that intake is more inhibited by
proteolysis intermediates, incl. biogenic amines, than ammonia per se
Silage intake is most influenced by
acids produced
VFA relative influences on intake:
▪ acetic acid -1,0
▪ propionic acid -5,4
▪ butyric acid -1,6
the sum of the produced acids (incl. lactate) is important. if their amount exceeds 130 g/kg in DM, intake starts to
decrease
Intensely fermented (biological inoculant) silage
digestibility and feed intake is usually what? compared to extensively fermented
(acidic preservative) silage digestibility?
lower than the extensively fermented
(acidic preservative) silage digestibility
The faster the silage pH decreases, the higher the
silage quality,
the lower the nutrient loss and
the higher the digestibility, and t
he higher the intake is (less acids).
The metabolic load is primarily related to the ability of the liver to
recycle the acids already produced in the silage
and produced from feeds during ruminal fermentation.
Each kilogram of concentrates in the feed ration reduces what?
silage dry matter intake
– in case of lucerne silage 0.5 kg, and
– in case of grasses 0.3kg
the wetter the silage, the greater the
depressive effect of the
concentrates
Cows can eat a good silage dry matter at 15
kg, with 10 kg concentrates added.
But if the silage is wet, what happens to its intake?
And how about if the silage is dryish?
If the silage is wet and they’re receiving 10 kg concentrate, silage intake will fall from 15 kg to
8 kg.
If in the same case the silage is dry, intake will fall from 15 kg to 12 kg.
This means wet silage with concentrates will have a depressive effect on intake and dry silage will not have quite as depressive an effect.
Concentrates will always have a bit of a depressive effect on silage intake. (I guess)
Feed intakes are controlled, in monogastric animals, by
the hormone insulin through the blood glucose level
Feed intakes are controlled, in ruminants, by
the rumen fill and the amount of ATP produced by oxidation of organic matter
What limits dry matter intake the most in practical feeding?
A. Ration energy
B. Ration crude protein
C. Ration mineral elements
A. Ration energy
Which feeds (DM) can dairy cows eat about 2% of their body weight of?
A. Roughages & concentrates -> ratio 60:40
B. Silage & concentrates -> ratio 50:50
C. Roughages & concentrates -> ratio 90:10
C. Roughages & concentrates -> ratio 90:10
Which hormones affect the body’s feeding
centre and stimulate eating?
A. leptin and ghrelin
B. insulin and gastrin
C. ghrelin and gastrin
D. leptin and insulin
C. ghrelin and gastrin
Which outside temperature ensures
maximum intake for cows?
A. -7…-10 °C
B. -5…+5 °C
C. +7…+10 °C
D. +15…+20 °C
C. +7…+10 °C
In which lactation stage is dairy cows feed
intake regulated by metabolic factors?
A. In far-off dry period
B. At the beginning of the lactation
C. In the middle of the lactation
D. At the end of lactation
B. At the beginning of lactation
In practice, in dairy cows feed intake is limited
at the beginning of lactation by the metabolic
load, and at the second half of the lactation by
the physical capacity of the rumen.
Which silage dry matter do cows eat the most?
A. 25-30%
B. 30-35%
C. 35-40%
D. 40-45%
D. 40-45%
Cows eat most silage when its dry matter content is 41.7%.
Which silage can cows eat more of?
A. Wilted with high amount of total acids
B. Wilted with low amount of total acids
C. Wet with high amount of total acids
D. Wet with low amount of total acids
B. Wilted with low amount of total acids
Cows eat 16% more wilted silage than unwilted silage.
When adding concentrates into the feed
ration the roughage intake …
A. decreases
B. increases
A. decreases
Each kilogram of concentrates in the feed ration reduces silage dry matter intake.
Oxidation of large amounts of organic
matter in the liver …
A. increases intake
B. decreases intake
B. decreases intake
Feed intake is controlled via the stimulation
intensity of the vagus nerve, this is determined by the amount of organic matter oxidised in the liver, and from this is produced ATP.
Reduced stimulation is associated with a perception of satiety (more organic matter -> more ATP -> do not eat).
