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2025 Exam Block 6 > Exam 2: Lecture 18 - Dairy nutrition 2 > Flashcards

Exam 2: Lecture 18 - Dairy nutrition 2 Flashcards

1
Q

what are the 4 goals of dairy nutrition

A
  1. maximize dry matter intake
  2. maximize energy intake
  3. preserve rumen health
  4. protect the transition cow
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2
Q

what is a transition cow

A

3 weeks before and after calving….important time to adjust diet to increase energy

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3
Q

what is beef cow maintenance DMI

A

about 2% DMI

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4
Q

what is lactating dairy cow maintenance DMI

A

about 3.5% - 4.5% DMI

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5
Q

what should the DMI/d of 1350lbs dairy cow at 3.7% be

A

50 lbs DM/d

(1350 lbs x 0.037)

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6
Q

what is DMI influenced by

A
  1. stage of lactation
  2. digestibility of fiber in diet
  3. environmental conditions
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7
Q

what lab measurement estimates digestibility of fiber?

A

ADF and NDF

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8
Q

how does rumen fill affect DMI

A

low digestibility = increased fiber = feel full = decreased DMI

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9
Q

how is DMI affected by level of production (lactating dairy cows})

A

stage of lactation increases energy for high milk production which increases amount eating

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10
Q

what does “DMI (% bw) = 120/NDF” mean

A

you can use NDF value of a feed to estimate DMI based on consumption of that feed

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11
Q

how many hours do cows spend eating a day

A

3-5 hours

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12
Q

how many hours do cows spend ruminating

A

at least 7-10 hours

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13
Q

how many hours do cows need to lay down and rest

A

at least 10 hours

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14
Q

what are the benefits of resting/lying down

A
  1. decreased energy expenditure and increased rumination
  2. decreased stress on feed = decreased # of lameness
  3. increased blood flow to udder
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15
Q

what happens if cows rest <10 hours/day

A

milk production decreases

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16
Q

what is perching and what does it mean

A

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

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17
Q

what is the recommended bunk space per cow

A

18-30 inches, space should allow about 70% of cows to eat at once

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18
Q

if there is 40 inches of bunk space/cow, what do we see with the cows

A

57% fewer aggressive interactions and 24% increase in feeding activity in 90 mins after feeding

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19
Q

for every additional 1lbs of DM eaten, ___1______ lbs more ___2___

A
  1. 2.5-3 lbs
  2. milk
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20
Q

what are the nutrients needed for dairy cows

A
  1. energy sources
  2. protein
  3. minerals esp Ca, P, Mg
  4. vitamins
  5. water
  6. fiber
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21
Q

why do cows need long fibers (important!!)

A

long fibers to stimulate rumination

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22
Q

what are the ADFs for dairy cows

A

lignin and cellulose

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23
Q

what are the NDFs for dairy cows

A

lignin, cellulose, hemicellulose, pectins

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24
Q

what are non-structural carbs (NSC)

A

starch and sugars

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25
what VFAs does the rumen produce
acetate, propionate, butyrate
26
what VFA is usually the highest in the ruminant
acetate
27
__1____ starch = ____2____ propionate
1. starch 2. propionate
28
what VFA is the main glucose precursor
propionate
29
acetate is mainly from structural __1___ and main precursor for ___2___
1. structural CHO 2. precursor for fat
30
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
31
what is acetate the precursor for
fat and acetoacetate (ketone)
32
what is propionate the precursor for
glucose
33
what is butyrate the precursor for
beta-hydroxybutyrate (ketone)
34
what does adipose tissue provide during lipolysis
free fatty acids
35
what does NEm stand for
net energy for maintenance
36
what does NEl stand for
net energy for lactation
37
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%
38
cows need a minimum of __1__ to __1_ % of forage particles to be over __2_ inches to stimulate rumination
1. 15-20% 2. 1.5 inches
39
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%
40
what is minimum peNDF
22%
41
why is rumen pH usually stable
1. VFAs are rapidly absorbed by papillae on rumen wall 2. bicarb in saliva buffers the rumen pH
42
what is SARA
subacute rumen acidosis
43
what happens with the development of subacute rumen acidosis
1. more common in dairy vs beef 2. prolonged periods of decreased rumen pH to 5.2-5.6 3. VFAs accumulate but not persistent lactic acid production
44
how is SARA and peNDF related
insufficient peNDF reduces salivary production of buffer
45
what is a normal rumen pH fluctuation
0.5-1 pH units within 24 hour period
46
47
what happens if pH falls below 5.5
DMI will decrease and a protective mechanism will be put in place
48
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
49
what is the relationship between ambient temp and rumen pH
1. dairy cattle cant dissipate heat efficiently 2. produce a lot of heat due to rumen fermentation 3. when temp and humidity are high they get heat stress 4. panting, decreased activity, refusal to lie down, drooling, reduced intake, thirst
50
what is soluble intake protein (SIP)
non-protein nitrogen NPN
51
what is metabolizable protein
protein available to the animal
52
what do SIP and DIP turn into during protein metabolism in ruminants
NH3 ammonia
53
what does ammonia turn into for protein metabolized in ruminants
bacterial protein which is then turned into metabolizable protein and also excreted
54
is SIP, DIP, or UIP readily available nitrogen for microbes?
SIP (soluble intake protein)
55
what does DIP (degradable intake protein) contain
true proteins that are more slowly digested in rumen/avail to microbes for a longer time period
56
what is UIP (undegradable intake protein)
protein that isnt rumen degradable but can be digested in the SI
57
why must we carefully balance dietary CHO and rumen degradable protein
because microbial protein synthesis requires energy!!
58
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
59
what is the amount of protein required for about 10 lbs of milk
1 lbs of protein per 10 lbs milk
60
cows utilize microbial protein for about _____ of protein requirement
50%
61
if cows use microbial protein for about 50% of the requirement, what do they still need to meet the remaining requirements
rumen undegradable protein
62
T/F: If NFC is high, you can substitute fat for some corn in diet
true!!
63
what % of fat do base rations have
3%
64
what is the maximum fat in ration
7% fat
65
T/F: fat is rumen undegradable
true!!
66
since fat is rumen undegradable, increased fat reduced ____ for microbial protein synthesis
CHO
67

2025 Exam Block 6 (22 decks)

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