Nutrition basics Flashcards
what is the rough capacity of the rumen?
> 200L
what type of fermentation occurs in the rumen?
anaerobic
where do the rumen microbes live in the rumen?
fibre mat (traps food and home to bugs)
what is the function of the primary rumen contraction?
mix the food to allow digestion
what is the function of the secondary rumen contraction?
eructation
what is the ratio of primary to secondary rumen contractions?
2 primary : 1 secondary
what do the rumen microbes break down food into?
volatile fatty acids
methane
carbon dioxide
what product of microbial fermentation do cows absorb for fat/glucose synthesis and energy?
VFAs
what is the order of constituents of the diet we think about when formulating or analysing a diet?
dry matter intake
energy
protein
minerals
vitamins
what DMI does a dry cow need in relation to bodyweight?
2% to 2.5%
what DMI does a lactating cow producing 25L of milk need in relation to bodyweight?
3%
what DMI does a lactating cow producing 50L of milk need in relation to bodyweight?
4%
what are some factors that influence DMI?
bodyweight/fatness
milk yield
stage of production
type of food (digestibility)
palatability, access, availability
social factors (bullying…)
stress, pain, disease, rumen health
what is metabolisable energy?
energy available to the cow for maintenance, growth, lactation and pregnancy
what are the units for metabolisable energy?
MJ/Kg DM
how is metabolisable energy calculated for feedstuffs?
using infra-red spectrometry data
what are the three fatty acids?
acetate
butyrate
propionate
what do microbes break down carbohydrates into?
volatile fatty acids
carbon dioxide
methane
how are the acids produced by the rumen buffered?
salivary bicarbonate and phosphate (from chewing the cud)
where are VFAs produced by the microbes absorbed?
by papillae across the rumen wall
what process turns VFAs into energy?
Krebs cycle
which VFA is used for glucose synthesis?
propionate
when are fats/oils used as part of a ruminants ration?
when the DMI fails to meet energy requirements in diets of high yielding cows
where are fats absorbed in ruminants?
small intestines
why do fats have to be fed as protected fats?
they need to bypass the rumen to be absorbed in the small intestine
why are cows in negative energy balance just after calving?
they have depressed DMI in the first weeks after calving which coincides with massive energy demand for milk production
what is the target for weight loss after calving?
don’t want to lose more than 0.5 - 1 BCS
what coping strategies do cows have for being in negative energy balance after calving?
eat more (increase DMI)
metabolise body fat and muscle
reduce milk yield
what is the rough maintenance energy requirement for a cow?
65 - 70 MJ
how much do you need to increase a cows energy requirements per litre of milk she’s producing?
5 MJ/L
what are the two divisions of crude protein?
rumen degradable protein
rumen undegradable protein
what is rumen degradable protein?
any nitrogen containing compound that is fermented in the rumen to produce ammonium which is used by the bugs for protein synthesis (growth)
what is rumen degradable protein broken down into?
NH4+
what could cause a high blood/milk urea?
insufficient metabolisable energy
excess rumen degradable protein in diet
how do ruminants digest protein?
rumen microbes digest proteins to NH4 which is used by microbes to grow and form microbial proteins, these are digested in the abomasum and small intestine
what happens to the ammonium from the RDP that isn’t absorbed by the microbes?
forms urea which is then excreted
how is rumen undegradable protein digested?
passes through the rumen and then digested in the abomasum and small intestine
what percentage protein is grass silage?
12-18%
why is maximising DMI important?
want to feed low energy density feeds because they will have more forage in them meaning healthier rumen microbes and a healthier cow (want to maximise DMI)
what is the aim for DMI at peak lactation?
4%
what is the aim for DMI intakes in the dry period?
12-14kg
what energy density should we aim for in a lactating cows diet?
11.5 - 12.3 MJ ME/Kg DM
what energy density should we aim for in a dry cows diet?
8.0 - 8.5 MJ ME/Kg DM
what is the dry matter of grass silage?
20-35%
what is the energy density of grass silage?
10-12 MJ ME/Kg DM
what is the energy density of maize silage?
11-11.5 MJ ME/Kg DM
what is the dry matter of maize silage?
30-35%
how much starch and protein in does maize silage compare?
starch is high
protein is low
can maize silage be used as fibre?
no - bad fibre source
what is the dry matter of bug bale silage?
30-35%
what is the energy density of big bale silage?
8.5 - 10.5 MJ ME/Kg DM
what is the dry matter of hay?
85%
what is the energy density of hay?
8-9 MJ ME/Kg DM
what is the dry matter of straw?
85%
what is the energy density of straw?
5.5-6.5 MJ ME/Kg DM
what is the dry matter of grass?
<20%
what is the energy density of grass?
10-12.5 MJ ME/Kg DM
what is the energy density of concentrates?
12.5 MJ ME/Kg DM
