Exam 2: Lecture 18 - Dairy nutrition 2 Flashcards
what are the 4 goals of dairy nutrition
- maximize dry matter intake
- maximize energy intake
- preserve rumen health
- protect the transition cow
what is a transition cow
3 weeks before and after calving….important time to adjust diet to increase energy
what is beef cow maintenance DMI
about 2% DMI
what is lactating dairy cow maintenance DMI
about 3.5% - 4.5% DMI
what should the DMI/d of 1350lbs dairy cow at 3.7% be
50 lbs DM/d
(1350 lbs x 0.037)
what is DMI influenced by
- stage of lactation
- digestibility of fiber in diet
- environmental conditions
what lab measurement estimates digestibility of fiber?
ADF and NDF
how does rumen fill affect DMI
low digestibility = increased fiber = feel full = decreased DMI
how is DMI affected by level of production (lactating dairy cows})
stage of lactation increases energy for high milk production which increases amount eating
what does “DMI (% bw) = 120/NDF” mean
you can use NDF value of a feed to estimate DMI based on consumption of that feed
how many hours do cows spend eating a day
3-5 hours
how many hours do cows spend ruminating
at least 7-10 hours
how many hours do cows need to lay down and rest
at least 10 hours
what are the benefits of resting/lying down
- decreased energy expenditure and increased rumination
- decreased stress on feed = decreased # of lameness
- increased blood flow to udder
what happens if cows rest <10 hours/day
milk production decreases
what is perching and what does it mean
perching = cows standing with front feed in stall, hind feet in alley or cows laying partially in the alley
means lameness, uncomfortable surface, short beds, and concern for udder contamination
what is the recommended bunk space per cow
18-30 inches, space should allow about 70% of cows to eat at once
if there is 40 inches of bunk space/cow, what do we see with the cows
57% fewer aggressive interactions and 24% increase in feeding activity in 90 mins after feeding
for every additional 1lbs of DM eaten, ___1______ lbs more ___2___
- 2.5-3 lbs
- milk
what are the nutrients needed for dairy cows
- energy sources
- protein
- minerals esp Ca, P, Mg
- vitamins
- water
- fiber
why do cows need long fibers (important!!)
long fibers to stimulate rumination
what are the ADFs for dairy cows
lignin and cellulose
what are the NDFs for dairy cows
lignin, cellulose, hemicellulose, pectins
what are non-structural carbs (NSC)
starch and sugars
what VFAs does the rumen produce
acetate, propionate, butyrate
what VFA is usually the highest in the ruminant
acetate
__1____ starch = ____2____ propionate
- starch
- propionate
what VFA is the main glucose precursor
propionate
acetate is mainly from structural __1___ and main precursor for ___2___
- structural CHO
- precursor for fat
what is the minimum amount of time cows should spend ruminating each day?
A. 4-6 hrs
B. 7-10 hrs
C. 3-5 hrs
D. 10-12 hrs
B. 7-10 hrs
what is acetate the precursor for
fat and acetoacetate (ketone)
what is propionate the precursor for
glucose
what is butyrate the precursor for
beta-hydroxybutyrate (ketone)
what does adipose tissue provide during lipolysis
free fatty acids
what does NEm stand for
net energy for maintenance
what does NEl stand for
net energy for lactation
for early lactation cows, what is minimum ADF, minimum total NDF, amount of NDF from forage, and NFC
minimum ADF - 19%
min total NDF - 28%
NDF from forage 20-24%
NFC = 37-42%
cows need a minimum of __1__ to __1_ % of forage particles to be over __2_ inches to stimulate rumination
- 15-20%
- 1.5 inches
for dry cows, what is minimum ADF, minimum total NDF, amount of NDF from forage, and NFC
min ADF - 28%
min total NDF - 35%
NDF from forage 25%
NFC = 20-30%
what is minimum peNDF
22%
why is rumen pH usually stable
- VFAs are rapidly absorbed by papillae on rumen wall
- bicarb in saliva buffers the rumen pH
what is SARA
subacute rumen acidosis
what happens with the development of subacute rumen acidosis
- more common in dairy vs beef
- prolonged periods of decreased rumen pH to 5.2-5.6
- VFAs accumulate but not persistent lactic acid production
how is SARA and peNDF related
insufficient peNDF reduces salivary production of buffer
what is a normal rumen pH fluctuation
0.5-1 pH units within 24 hour period
what happens if pH falls below 5.5
DMI will decrease and a protective mechanism will be put in place
what is the protective mechanism of the rumen for a drop in pH
osmoreceptors in rumen sense the drop in pH and will cause cow to stop eating
what is the relationship between ambient temp and rumen pH
- dairy cattle cant dissipate heat efficiently
- produce a lot of heat due to rumen fermentation
- when temp and humidity are high they get heat stress
- panting, decreased activity, refusal to lie down, drooling, reduced intake, thirst
what is soluble intake protein (SIP)
non-protein nitrogen NPN
what is metabolizable protein
protein available to the animal
what do SIP and DIP turn into during protein metabolism in ruminants
NH3 ammonia
what does ammonia turn into for protein metabolized in ruminants
bacterial protein which is then turned into metabolizable protein and also excreted
is SIP, DIP, or UIP readily available nitrogen for microbes?
SIP (soluble intake protein)
what does DIP (degradable intake protein) contain
true proteins that are more slowly digested in rumen/avail to microbes for a longer time period
what is UIP (undegradable intake protein)
protein that isnt rumen degradable but can be digested in the SI
why must we carefully balance dietary CHO and rumen degradable protein
because microbial protein synthesis requires energy!!
for which cow is subacute rumen acidosis a particular risk?
A. dry cow
B. pregnant
C. transition cow
D. cow in late lactation
C. transition cow
what is the amount of protein required for about 10 lbs of milk
1 lbs of protein per 10 lbs milk
cows utilize microbial protein for about _____ of protein requirement
50%
if cows use microbial protein for about 50% of the requirement, what do they still need to meet the remaining requirements
rumen undegradable protein
T/F: If NFC is high, you can substitute fat for some corn in diet
true!!
what % of fat do base rations have
3%
what is the maximum fat in ration
7% fat
T/F: fat is rumen undegradable
true!!
since fat is rumen undegradable, increased fat reduced ____ for microbial protein synthesis
CHO
