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7-Biology of Lactation > Slide Set 1: Biological Functions of Lactation > Flashcards

Slide Set 1: Biological Functions of Lactation Flashcards

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1
Q

What are the key charactestics of mammals?

A
  • 4000 species
  • Most of mammals are viviparous and possess hair
  • The only vertebrates to have a mammary gland
  • Feeding young by secretion from the mother
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2
Q

What are the animals that carry the mammalian characteristics but they are not mammals?

A
  • piscus fish (produces milk from their skin, they don’t produce regular milk but it is more like a mucous substance to feed their young)
  • pigeon, flamingo, emperor penguins
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3
Q

Pigeons secrete ___ milk

A

crop

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4
Q

What is crop?

A

Crop is a tissue between esophagus adn the top of the stomach. The main function of this region is to store food but 2 days before hatching the function of this tissue becomes producing milk.

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5
Q

What is the hormone that controls milk synthesis?

A

Prolactin

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6
Q

Prolactin is the msot important hormone for milk production in pigeons, rabbits, humand but NOT for _____

A

cows

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7
Q

What is the origin of the crop milk?

A

crop sloughed epithelial cells

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8
Q

What is the compostion of crop milk like?

A 
Protein = 60%
Fat = 30-35%
CHO = 1-3%

No casein
No lactose

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9
Q

Baby pigeons are called

A

squabs

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10
Q

What determines the volume of milk?

A

High lactose means more diluted milk, lactose is responsible for the volume of the milk

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11
Q

How long does the laction lasts in pigeons?

A

10 days

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12
Q

What are the 2 subclasses of mammals?

A

Protheria (no placenta)

Theria (placenta)

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13
Q

What is the order of protehria?

A

monotemata (egg-laying mammals)

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14
Q

What are the 2 infa-classes of theria?

A
  • metatheria (marsupials)

- eutheria (true placentals)

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15
Q

What are the key characteristics of metatherians?

A
  • viviparous
  • very immature young
  • poorly developped placenta
  • long lactation
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16
Q

What are the key characteristics of monotremes?

A
  • Only two species still exist (Australia)
  • Egg laying mammals (oviparous) - no placenta
  • No placenta & mammary glands have no teats
  • Young very immature and rely totally on milk
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17
Q

What are the two monotremes that still exist?

A
  • Echidna (Spiny anteater)

- Duckbill platypus

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18
Q

What are the key characteristics of Echidna’s eggs?

A
  • Eggs laid ~30 days after ovulation (single egg)
  • Eggs incubated inside a pouch (10 days)
  • Hatched young & very immature
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19
Q

How and when is echidna born?

A

After 10 days, young pierces egg shell with egg tooth

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20
Q

What are the key characteristics of a newborn echidna?

A

– 1⁄2 inch long

– Hind legs buds, front legs and toes well formed with tiny transparent claws for gripping the pouch hair

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21
Q

What are the key characteristics in lactation of echidna?

A
  • Milk oozes into a depression within the pouch

* Suckling period for the young ~ 200 d

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22
Q

Explain the life cycle of a young echidna

A
  • Carried in the pouch for ~ 53 days
  • Suckles its mother once every 5 days
  • May drink up to 20% of its body weight in milk daily
  • Grows fast (from 0.5 g to 200 g in 2 months )
  • When spines begin to appear, young is placed in a nursing burrow
  • Leaves the burrow ~ 5 months and is weaned 4 weeks later
  • Becomes independent ~ 1 year
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23
Q

What are the key characteristics of Duckbill platypus’ eggs?

A

• Lays 2 eggs 15 d after mating
• Eggs incubated in a burrow and
hatched in 10 to 14 d
• Hatched young are very immature

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24
Q

What are the key characteristics in lactation of duckbill platypus?

A
  • Suckling period for the young ~100 d
  • Milk oozes into stiff hairs in the abdomen
  • Young suckles milk off stiff mammary hair on abdomen
  • Young can take up to 20% of its body weight in 2 hours
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25
Q

What are the key characteristics of the mammary gland of duckbill platypus?

A
  • Mammary glands are located on each side of the midline of the abdominal wall
  • 100-150 separate glands composed of simple branched convoluted tubes
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26
Q

What are the key characteristics of Marsupials (Metatheria) in terms of young bearing, birth, mammary gland and lactation period?

A

☛ Viviparous & have short gestation period (3-6 weeks)
☛ Give birth to very immature young
☛ Mammary gland more developed than in monotremes
☛ Mammary glands have teats (up to 20)
☛ Long suckling period (50-550days)

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27
Q

What is so unique about Marsupial lactation?

A
  • Drastic changes in milk composition over lactation period
    early lactation vs late lactation
  • Asynchronous lactation
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28
Q

What are the features of the early lactation milk in marsupials?

A

☛ Early lactation (parturition to 200 days):

☛ Simple milk high in carbohydrates (mainly oligosaccharides) and low protein and fat

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29
Q

What are the features of the late lactation milk in marsupials?

A

☛ Late lactation 200 to 330 days):

☛ Complex milk low in carbohydrates and high in fat

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30
Q

What is asynchronous lactation?

A

☛ Adjacent mammary gland produce milk of different composition
☛ Some glands can be lactating while other are regressing

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31
Q

Explain the sexual maturity and breeding in Tammar Wallaby (marsupial)

A
  • The female reaches sexual maturity at approximately 9 months of age.
  • Males become sexually mature at 2 years of age.
  • Female can be constantly pregnant from 1st pregnancy until death
  • Strict seasonal patterns of breeding, young are born between January and March.
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32
Q

Explain the gestation of tammar wallaby

A
  • Female wallabies give birth to young (joey) but lack a true placenta. Therefore young are very immature at birth.
  • The female kangaroo can support three offspring, each at a different stage of development
  • Gestation lasts between 25-28 days.
  • Young weighs between 350-400mg at birth (0.01% of mother’s body weight).
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33
Q

Explain how tammar wallaby can raise 3 offspring at one time

A

– Joey #1: lactation (outside pouch, ~1.5 years)
– Joey #2: lactation (inside pouch, ~9 months)
– Joey #3: held in embryonic diapause

34
Q

What is the first sign of birth in tammar wallaby?

A
  • First sign of the female about to give birth is the cleaning of the pouch.
  • Birth posture is also very specific.
35
Q

What happens after the birth of tammar wallaby?

A
  • Once the neonate is born it takes about 15 seconds before it starts climbing to the pouch.
  • Duration of the climb is 2-3 minutes.
36
Q

How does tammar wallaby climb inside the pouch?

A

• Hair extending from the cloaca to the pouch grows upwards to facilitate the climb to the neonate.

37
Q

What happens to the mother tammar wallaby once she gives birth?

A

• After giving birth the female mates again, however this embryo will remain dormant until the joey begins to leave the pouch.

38
Q

How is the pouch maintained for Joey?

A
  • Once the joey is in the pouch, the mother ensures that it is clean.
  • She removes the brown waxy substance being secreted but she is also ingesting the feces and the urine of the joey.
  • The waxy substance will be recycled back into milk for the nursing.
39
Q

What is the life inside the pouch like for Joey? What is the timeline is like?

A
  • Once inside the pouch, the neonate attaches to one of the 4 teats.
  • Once the teat is inside the joey’s mouth it expands locking it firmly into place.
  • Whichever teat it chooses will continue to develop.
  • The remaining teats will undergo involution and/or produce milk with different composition.
  • The joey then remains attached to this specific teat for 100 days.
  • After this period the joey should weigh 100g.
  • At 180 days the joey is now able to pull its head out of the pouch and starts to nibble on grass.
  • At 190 days the joey begins to leave the pouch for short periods of time.
40
Q

What is the overview of a timeline of joey from day 70 to 350?

A
  • 70-day old joey (still in the pouch)
  • 150-day old joey (still in the pouch), eyes open at day 140, under hair visible
  • 200-day old joey (stay outside the pouch, but still nurse for few weeks), able to stand and urinate at day 160, thermoregulation at day 180
  • At 250 days the joey leaves the pouch permanently.
  • It can return to suckle from a protruding teat.
  • Milk yield peaks at day 240
  • The decline in frequency of suckling coincides with a 2nd joey being born.
  • Between 300-350 the joey ceases to suckle completely
41
Q

What are the key characteristics of Eutherians?

A

☛ 95% of mammals, viviparous and more diverse
☛ Young develop and grow in utero (True placenta)
☛ Mammary glands have teats
☛Young are born more mature than the marsupials

42
Q

Evaluate eutherians in terms of gestation, neonate weight and lactation

A

☛ Gestation: 22 d (shrew) to 660 d (African elephant)
☛ Neonate weight: 7 g (shrew) to 5 tons (whales)
☛ Lactation (nursing): 5 d (fur seal) to 900 d (orangutan)

43
Q

Compare metatherians and eutherians

A

Metatherians
• Rely more on lactation
• Gestation represents only
12% of the time between conception and weaning
• Paternal invest at birth smaller than eutherians
• Total maternal invest
similar to eutherians

Eutherians
• Rely more on gestation
• Gestation represents > 50% of time between conception and weaning
• Paternal invest at birth larger than marsupials
• Total maternal invest
similar to marsupials

44
Q

What are the similarities between metatheria and monotremata

A
  • milk composition changes significantly during lactation
  • simple milk during early lactation
  • nutrient-dense milk later in lactation
45
Q

What is the 2 major roles of lactation?

A

☛ Milk production is only one function of lactation

☛ Parent offspring bond is a vital function of lactation

46
Q

What are the benefits of lactation?

A
  • Defense against predators
  • Educational opportunity
  • Social facilitation
47
Q

What are the other roles of lactation?

A
  • fertility control
  • thermoregulation
  • nutrition
  • immunological functions
  • physical protection
  • protection, learnt skills
48
Q

What is reproductive investment?

A

Time between conception & weaning

49
Q

Reproductive investment of mammals include:

A
  • Pregnancy
  • Lactation
  • As a general role, lactation occupies ~50% (40-60%) of time between conception and weaning (fairly constant among mammals)
  • The role does not apply for mammals with very short or very long lactation (e.g. in marsupials 75-95%)
50
Q

What is the relationship between lactation and reproduction

A
  • Physiology of lactation is closely linked to physiology of reproduction
  • the female cannot produce milk without being pregnant and giving birth
  • the way the hormones are controlled in reproduction the same way the hormones are controlled in lactation
51
Q

What does lactation strategy mean?

A

Lactation strategies represent different adaptive solutions to different problems

52
Q

What are different lactation strategies?

A 
☛ Litter size
☛ Degree of young development at birth
☛ Length of gestation
☛ Length of lactation
☛ Growth rate of the young
☛ Kind and extent of parental care
☛ The fraction of total growth contributed to milk
53
Q

Differences in lactational strategies are reflected on:

A

☛ Milk quantity
☛ Milk composition
☛ Frequency and duration of suckling
☛ Time until weaning

54
Q

How does litter size affect lactation strategy?

A

☛ Varies by species from 1 to 20
☛ Large litters are usually altricial while small litters are either precocial or altricial
☛ Demand on mother for nutrition is higher for large litter size

55
Q

How does length of lactation affect the lactation strategy?

A

☛ Range from 4-5 d (hooded seals) to 900 d (chimpanzees)
☛ ~50% of lactations range from 30-135 d
☛ Lactations are longer for prototherians (av. 150 d) & metatherians (av. 120 d) than for eutherians (av. 50 d)
☛ Lactation lengths are longest for eutherians
☛ Short lactations (< 10 d) are rare but long lactations (> 500 d) are common in large-bodied mammals

56
Q

What is the relationship between the length of lactation and the adult female mass?

A

☛ Positive correlation.
☛ Exceptions include: earless seal, baleen whale
☛ Possible justification for long lactation in some mammals:
A- Marsupials: Very immature young
B- Primates: Extensive psychosocial development
C- Bats: Extensive neuromuscular co-ordination required for food acquisition in flight

57
Q

Which mammals have short lactation period?

A

Earless seal & baleen whale

58
Q

Which mammals have long lactation period?

A

Marsupials, primates, bats

59
Q

Which mammals have intermediate lactation period?

A

Other eutherians

60
Q

What are the types of nursing habits? Give examples

A

A- Animals nursing on demand: marsupials, primates, perissodactyls (odd-toed), some artiodactyls (even-toed)
B- Animals nursing on schedule: rodents, many carnivores, many artiodactyls
C- Others: seals (harp and hooded seals), bears, whales

61
Q

What does nursing on demand mean?

A

also known as feeding “on cue” and “baby-led” feeding—-is about responding flexibly to your baby’s hunger cues. It means initiating feedings when the baby requests them, and continuing each feeding session until the baby is satisfied.

62
Q

What does nursing on schedule mean?

A

the mother determines the time of the milk ejection (herbivores)

63
Q

Compare the nutrient content in milks of nursing on demand and nursing on schedule

A

☛ Animals nurse on demand tend to produce milk with lower nutrient content than those nurse on schedule

64
Q

Compare the solids concentrations in milks of nursing on demand and nursing on schedule

A

Other (higher fat) > Nursing on schedule > Nursing on demand (carbohydrates and ash constitutes > 50 of
milk total solids)

65
Q

What type of young nurses on demand?

A

Precocial young tend to nurse on demand

66
Q

What type of young nurse on schedule?

A

Nest-building animals nurse on schedule

67
Q

What are the types of young?

A
  • Altricial young

- Precocial young

68
Q

What are the key characteristics of altricial young?

A

• Very immature young
• Born after short gestation (not all the time)
• Born in large litters
• Nurse on schedule or on demand
• Include marsupials, monotremes & some eutherians
ex: dog, cat, lions, rats, mice

69
Q

What are the key characteristics of precocial young?

A 
• Mature young
• Born after long gestation (not all the time)
• Nurse on demand
(some exceptions)
• Born in small litters
• Include some eutherians
70
Q

What are the two other classifications of eutherians?

A
  • Monotocous eutherians

- Polytocous eutherians

71
Q

What are the key characteristics of monotocous eutherians?

A

☛ Give birth to precocial young
☛ Small offspring relative to adult mass
☛ Gestation & lactation are not concurrent
☛ Young are furred, mobile, but they remain with their mothers for long periods
☛ Young eat solid food early in lactation

72
Q

What are the key characteristics of polytocous eutherians?

A

☛ Give birth to altricial or semi-altricial young
☛ Litter mass relative to adult mass can be small or large
☛ Gestation & lactation are commonly concurrent
☛ Young eat solid food usually late in lactation

73
Q

What is the caloric value of milk in terms of macronutrients?

A

Fat 9.11 kcal/g
Protein 5.86 kcal/g
Carbohydrates (lactose) 3.95 kcal/g

☛ Due to incomplete digestion & absorption, the following values (metabolic values) are used
Fat = 9, protein 4 and carbohydrates 4 kcal/g

74
Q

True/False

Ash (minerals) has no caloric value

A

true

75
Q

Give examples of comparison of the caloric energy content of milk in different mammals

A

fur seal > dolphin > Echidna > bat > red kangaroo > human > cow > donkey

76
Q

What does caloric value of milk reflect?

A

☛ The low caloric content of primate and ungulate milk may reflect the alternative functions (social & protective) of lactation in these mammals

77
Q

What does high caloric value of milk indicate?

A

☛ Milk with high caloric value (e.g. seals, whales) may have a thermo-regulatory function for altricial young who are unable to regulate their body temp.

78
Q

Milk energy transfer from the mother to young depends:

A

1- Maternal body weight
2- Energy requirement of young (related to litter size)
Strong relationship exists between energy secreted in milk (peak lactation) & maternal body wt

79
Q

What are the two equations that show the relationship between the energy secreted in milk and the maternal body weight?

A 
E = 175 Wm0.81 (species with large litter) 
E = 83 Wm0.73 (species with single young)
E = milk energy output (kcal/d)
80
Q

What is the equation that shows the amount of energy secreted in milk is directly proportional to the litter size and the maternal body wt?

A

Energy milk output (kcal/d) = 225nWm0.83
n = # of young
Wm = maternal body wt.

81
Q

What is the location of the mammary gland?

A

Ventral and lateral to the midline of the abdomen

82
Q

What is Simple vs Complex Mammary gland?

A

Simple gland: Milk empties through a single opening or orifice at the surface.

Complex gland: May have multiple openings, each draining a functionally separate simple gland.

7-Biology of Lactation (16 decks)

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