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Physiology of Lactation > Post Quiz 6 > Flashcards

Post Quiz 6 Flashcards

1
Q

What are the advantages of AMS?

A

Increase milk yield over 2X (11%)
More time to manage information
Free-up labor for other activities:
– additional cropping
– off-farm employment
Less stress (cows/humans)
Improved life-style
Enhance viability of small farms (labor, environment, etc.)

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2
Q

Parlors represent what percent of new facility costs?

A

30-50%

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3
Q

What factors are important in optimizing the use of parlors?

A

Parlor turn-around time
* 1st cows in quickly
* All units attached in 4-5 minutes
* 4.5 - 5 cow-changes/hr
– 12 min/side
* Dictates total milking time

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4
Q

What Factors are important in parlor efficiency?

A

Optimizing Use
Premilking Hygine
Batch/ territorial vs. alternating milking scheme
Mechanization
Milk Yield Per Cow

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5
Q

How does premilking hygine impact parlor efficiency

A

Affects # milkers/stalls
– Routines:
* Minimal: strip, wipe, attach (14 sec)
* Full: strip, predip, wipe, attach (30 sec)
– Predipping costs time/cow flow (but reduces new IMI)
– Dirty cows: costs cow flow; more mastitis, SCC

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6
Q

How does Batch/Territorial vs. Alternating milking Schemes affect parlor efficiency

A

Batch milking costs ~ 25% reduction in cow flow
* 1st cows easiest; last cows rushed
* Disrupts routine
* Goal is all units attached in 4-5 min

Employee breaks:
* 15 - 30 min breaks every 4 hrs reduces total milking time

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7
Q

How does mechanization impact parlor efficiency?

A

View mechanization as replacing people or reducing milking time
* ATO, rapid exit, crowd gates, indexing, sort gates all increase
throughput by 5 - 10% each!

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8
Q

How does milk yield per cow impact parlor efficiency

A

Slow-milking cows reduce throughput
* Herringbone
* Parallel (gang exit)
* Rotaries
* Remember continued increases in milk production lead to
increased milking time per cow
* 3X cows milk out faster
– 3X may add only 10% to total milking time

Group cows:
– Stage of lactation approximates milking speed

Size groups to parlor
– Less partial loading
– Holding area; 1 hr. capacity
– 15-20 sq.ft./ cow

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9
Q

What Factors Affect Milk Yield

A

Secretion Rate
Milking Frequency
Milking Intervals
Dry Period Management
Photoperiod
Heat Stress
Mastitis

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10
Q

What impacts secretion rate of milk by the mammary system?

A

amount of healthy parenchymal tissue
-genetics, udder development; mastitis

rate of secretion per unit of tissue
-genetics, precursors; secretion rate is inversely related to alveolar pressure

Milk is secreted constantly, but removed periodically:
–secretion rate is influenced by products already secreted
–yield will equal capacity to secrete + capacity to store product

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11
Q

What does the total amount of milk accumulated in the gland depend on?

A

secretion rate; a function of intramammary pressure
and
time; the rate decreases with time as pressure increases

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12
Q

How long does it take for milk synthesis to cease after milking

A

Approximately 36 hours

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13
Q

How does milking frequency impact milk yield?

A

More frequent milk removal :
–increases average secretion rate for given time period
–increases total yield for given period
–has dramatic effect on total lactation yield

Major increase in yield is due to decline in alveolar pressure (increased average secretion rate)
–some increase may be due to:
*greater feeding frequency
*reduced mastitis; SCC

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14
Q

What impact does 3x Milking have on Milk Yield compared to 2x?

A

Increases lactation yields ~15 - 20% compared to 2x milking
under similar management conditions

DHI standardized lactation correction factor for 3x herds = 0.85

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15
Q

How does milking interval impact milk yield?

A

Constant equal milking intervals optimize average secretion rates and allow maximum yields:

For 2x herds; effect of uneven milking intervals:
Interval ——- Decline in yield
9 : 15 ———–2%
8 : 16 ———–4%

Average secretion rate is not adversely affected until ~14 hrs after milk removal

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16
Q

What is the impact of long term imbalances in milking intervals?

A

speeds involution
AND
decreases persistency & milk yield

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17
Q

What is the relationship between milking interval and lactation number?

A

Younger cows (first lactation) recieve greater benefits from shorter milking intervals

1st lactation cows respond more dramatically to 3x milking than older cows

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18
Q

What happens if you milk cows 1x during their last three months of lactation

A

Decreased milk yield 38% for last 3 mo.
Decreased lactation yield 12%
increased fat %
cattle dried off 12 days earlier (gradual; not recommended!)

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19
Q

What happens if you milk cows 1x for the entire lactation?

A

1st lactation cows declined 50% in lactation yield
Older cows declined 40% in lactation yield

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20
Q

What happens if you milk 13x per week (skip one milking per week)?

A

1st lactation cows declined 11% in lactation yield
older cows declined 5% in lactation yield

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21
Q

What is involution?

A

natural regression of the mammary gland after peak lactation (most dramatically after dryoff)

after peak lactation, milk yield drops ~ 5% month

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22
Q

What happens during mammary gland involution?

A

Cellular metabolic activity slows
Secretion rate/ cell declines
Size & number of alveoli decline
Number of cells/alveolus decline
Proportion of connective tissue increases
Mammary gland DNA content declines

Biochemical changes:
–decreased fatty acid, acetate, glucose incorporation into lipid
–reduced mitochondrial function
– reduced oxidation of glucose; reduced ATP

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23
Q

What factors accelerate involution?

A

cessation of suckling/ milk removal accelerates involution (dry period, mastitis treatment)

cessation of milk removal increases alveolar pressure:
*accumulation of product
*disruption of microtubule transport
*disruption of alveolar walls ( myoepithelial cells remain intact)
*increased SCC

24
Q

What factors retard involution?

A

Routine oxytocin administration
PRL, STH, T3, T4 retard involution
Continued milking/suckling stimulus
–provides physical/endocrine stimulus
–neurostimulation (milking/suckling stimulus)
*increases PRL, ACTH
*frequent milk removal serves to keep mammary pressure low

25
Q

What affect does the lack of a dry period have on milk yield?

A

Lack of a dry period reduces next lactation yield by 25-33%

26
Q

How does the length of the dry period impact milk yield?

A

dry periods less than 40 days and more than 60 days result in decreased lactation yield

dry periods longer than 45 days do not increase lactation yield

short dry periods result in lack of complete epithelial cell regeneration

27
Q

What is photoperiod?

A

length of time cattle are exposed to light

28
Q

What affect does Photoperiod have on milk yield?

A

18hr light/ 6hr dark (long day length) is best for maximum yields during lactation

8hr light/16hr dark (short day length) is best during 60 day dry period

29
Q

What hormonal affect does long day have on lactating dairy cows?

A

Long day length suppresses melatonin (from pineal gland)
–melatonin apparently regulates (suppresses) IGF-1 release from liver
– IGF-1 increases milk synthesis
– long day length allows greater IGF-1 stimulation of milk
synthesis (~ 5 lbs/cow/day = ~ 7 %)

30
Q

How does a 24 hour light period effect lactation?

A

A 24 hour light period does not give a photoperiod response as a short dark period is necessary

31
Q

What affects does a long day length have on milk yield and DMI?

A

Long day increases milk yield and DMI

32
Q

What impact does a short day length during the dry period have on the next lactation milk yield

A

Milk yield was increased in cattle which were subjected to short day length (8hr light/16hr dark) during the 60 day dry period

33
Q

What degree of darkness or lightness is required for each phase of the photoperiod

A

Light Period = Greater than or equal to 20 foot-candles of illumination
Dark Period = No more than 5 foot candles for 30 minutes, really need complete uninturupted darkness

34
Q

What impact does heat stress have on milk production

A

As of 2003,
*$2.4 Billion in losses annually (All species, no abatement)
*$1.7 Billion with abatement
*$897 Million in the dairy industry
– Reduced Animal Performance
– Reduced Reproductive ability
– Increased Mortality

Average cow spends 14.1% of time heat stressed

In Virginia:
Decreased DMI (311 kg/cow/year)
Decreased Milk Yield (627 kg/cow/year)
Increased Days Open (22.3 d/cow/year)

1,585 heat stress hours annually
-> 300 hours above the U.S. Average

35
Q

What factors impact heat stress conditions?

A

Air Temperature
Relative Humidity
Solar Radiation
Air Movement
Precipitation

Heat stress conditions are first observed at a THI of 68

36
Q

What affects does high temperature and humidity have on the cow?

A

Reduces ability to dissipate heat
Increases respiratory/cardiac rate (100F = ~5x increase)
Reduces DMI (cessation @ 105F, > 50% humidity)
Reduced rumination

These factors cause reduced milk yield

37
Q

How do low temperatures affect dairy cattle?

A

Increased body maintenance requirement
Increased DMI
Reduced milk yield if extra energy and feed quality not maintained (frozen feed/water reduces DMI)

38
Q

How does wind speed relate to heat stress?

A

Increasing wind speed in times of heat stress can minimize the effects of heat stress and raise production closer to non heat stressed levels

39
Q

What is the relationship between breed and heat stress?

A

Heat tolerance varies among breeds:
Holstein & Swiss become heat stressed around 80F
Jerseys become heat stressed around 85 Degrees F
Brahman and Water Buffalo can tolerate up to approximately 95 degrees F

40
Q

What methods can be used to reduce heat stress in dairy cattle?

A

Shade structures, screens, trees (control environmental mastitis)
–Shade cloth:
*inexpensive
*portable
*replacement cost

Reduce radiant heat
Increase evaporative cooling
Sprinklers, misters

Structures
*Metal roofs (white)
*Open sided
*12 - 16 ft eaves; ridge vent
*Fans, w/misters/soakers
*Orientation (N/S)?; wind direction (E/W)? (depends on location)
*Shade cloth?

Cool feed areas
*Encourage cows to eat

41
Q

In addition to the pens, what other areas should heat abatement be managed?

A

Holding Pens

42
Q

Effects of reducing heat stress?

A

Reducing Heat Stress:
–Fans, sprinklers, misters
*reduce body temp
*increase DMI
*increase reproductive performance
–increase # heats
–increase embryo survival

Utilize night cooling
*temp > 70F

Measures to improve cooling improve milk yield by 10 - 12%

43
Q

What affect does mastitis have on milk production?

A

Clinical & subclinical mastitis reduces milk yield and all valuable components
*Reduced:
–total yield
–casein
–fat
–lactose
–Ca, P

44
Q

What is the relationship between SCS and Milk Yield

A

Begining at a SCS of 3, there is approximately a 1.5 pound per day decrease in milk yield for every 1.0 increase in SCS for older cows

For first lactation cows it is about a 0.75 pound per cow decrease

45
Q

What are the two metabolic hormone actions?

A

Anabolic
or
Catabolic

46
Q

Anabolic

A

Generally enhance target tissue function and/or nutrient uptake
–increased uptake of amino acids, glucose, fatty acids
–increased incorporation of :
»Amino acids into protein
»Glucose into glycogen
»Fatty acids into adipose tissue
Example: insulin

47
Q

Catabolic

A

Generally stimulates breakdown (catabolism) and/ or release of nutrients from target tissues,
OR
Retards uptake of nutrients by storage tissues
»Decreased glucose, amino acids, fatty acids uptake by storage tissue
» Increased lypolysis , glycogenolysis , gluconeogenisis
Example: glucagon

48
Q

Anabolic Hormones

A

STH (GH)
insulin
calcitonin

49
Q

Catabolic Hormones

A

STH (GH)
glucagon
cortisol
T3, T4
PTH
epinephrine

50
Q

Anterior Pituitary Hormones

A

Protein Hormones

ACTH - adrenal cortex - cortisol - Prolactin binding, protein synthesis

FSH - follicle - estrogen - mammogenesis

LH - follicle - CL - progesterone - mammogenesis

PRL - mammary cell protein synthesis

TSH - thyroid - T3, T4 (thyroxin) - cellular metabolism

51
Q

Growth Hormone

A

Growth hormone (GH, STH)(anabolic & catabolic)
*GH can act on liver, fat, bone, muscle, etc.
*GH:
–increases protein synthesis
–affects metabolism (anabolic & catabolic)
–stimulates growth factors (IGF’s from liver)
–synergizes with E2 , P4 , PRL
–anatagonistic to insulin (stimulates gluconeogenesis, lipolysis)

52
Q

Parathyroid Gland Hormones

A

Protein hormones
(regulates calcium metabolism)

Calcitonin (anabolic)
*acts on osteocytes - calcium absorption - decreases blood calcium

Parathyroid hormone (PTH )(catabolic)
*acts on osteocytes - calcium resorption - increases blood
calcium
*acts on kidney - depresses calcium excretion; stimulates vitamin D conversion - increases gut calcium uptake

53
Q

Adrenal Cortex Hormones

A

Steroid hormones
Cortisol
*stimulated by ACTH (ant. pit.)
*synergizes with PRL (ant. pit) to enhance protein synthesis in mammary cells
* chronic release (stress) causes depression of immune response (depresses WBC)
* chronic release has catabolic (glycogenolytic) effect on metabolism

54
Q

Adrenal Medulla Hormones

A

Protein hormones
– Epinephrine, Norepinephrine (adrenalin, noradrenalin)
* increases as result of acute stress (sympathetic stimulation)
*causes vasoconstriction, contraction of teat sphincter in MG
*blocks myoepithelial cell oxytocin receptors
*catabolic ( lipolytic ) effect on metabolism

55
Q

Thyroid Gland Hormones

A

Protein Hormones
–Triiodothyronine (T3), Thyroxine (T4) (injected; short acting)
* increase rate of cellular metabolism (BMR)
* increase cellular O2 consumption and energy production
* increase protein synthesis
* catabolic effect on metabolism ( glycogenolytic , lipolytic)
*early lactation, increases yield 10%
*late lactation, increases yield 15 - 20%

–Thyroprotein (iodinated casein; fed)
*increases yields ~ 2 - 4 months; then decline
*older, high yielding cows respond best
*removal is followed by abrupt decline in yield
*fed only to cows in positive energy balance
*DMI increase is crucial
*increases PRL
*eventually lowers cortisol availability (increases Corticosteriod Binding Globulin)

56
Q

Pancreas Hormones

A

Insulin (beta cells)
*Increases cellular glucose uptake
*Increases cellular aa uptake
*Increases lipogenesis & glycogenesis
*Anabolic to adipose, muscle tissue
*Decreases blood glucose concentration

Glucagon (alpha cells)
*Increases lipolysis
*Increases glycogenolysis
*Depresses cellular glucose uptake
*Catabolic to adipose, muscle, liver tissue
*Increases blood glucose concentration

Physiology of Lactation (8 decks)

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