This document discusses lactation in various mammals. It begins by explaining that lactation is controlled by hormones like prolactin and oxytocin and provides nutrition and immunity to young. It then covers characteristics of different subclasses of mammals - monotremes lay eggs but secrete milk, marsupials give birth to underdeveloped young that nurse in pouches, and placentals have fully developed young. Specific examples of lactation in platypuses, koalas, kangaroos, mice, cats and humans are provided, describing milk composition, nursing behaviors, and length of lactation periods.

1. Lactation in Mammals
Prepared By : Irsa Ikhlaq

2. • Lactation
 Lactation is an essential feature of female mammals.
 Lactation is under endocrine control.
 The two main hormones involved are prolactin and oxytocin.
Lactogenesis, or the process of changes to the mammary glands
to begin producing milk, begins during the late stages of
pregnancy.
 The chief function of lactation is to provide nutrition and immune
protection to the young after birth.
 Lactation is the characteristic feature of mammals

3. • Class Mammalia
 The Mammalia class is made up of 5000 species of vertebrates.
 The main difference between mammals and other vertebrates are
three characteristics: hair, milk production in mammary glands,
and three bones in the inner ear.
 Extant mammals are divided into three subclasses based on
reproductive techniques (monotremes, marsupials, and placentals)
 Infra-Class Monotremes
 Monotremes are made up of only five species:
 the platypus and other four species.
 They are egg-laying mammals.

4. • Duck-billed Platypus reproduction and
lactation
 After an egg hatches, the tiny baby (called a puggle) drinks its
mothers milk, which comes from tiny openings in the mothers
belly through ducts.
 Duck-billed Platypuses have a life span of 10 – 17 years.
 Infraclass Marsupials
 Marsupial mammals give birth to babies that are not completely
developed. .
 Koalas, kangaroos, wallabies, and opossums are some of the
better-known marsupials

5. • Introduction to Koala
 Scientific name of Koala is Phascolarctos cinereus. Phacolarctos
comes from two Greek words: ‘phaskolos’ meaning pouch and
‘arktos’ meaning bear and cinereus means ash-coloured (grey).
 The koala is an iconic Australian animal often called the koala
“bear,” But they are not bear.
 Mammary glands
 In marsupials, the mammary glands, which vary in
number, are located within the pouch and terminate in a
teat.

6. • Lactation period in koala
 The production of milk by lactating females and energy expenditure
and foliage intake of their dependent young, were investigated in free-
ranging koalas.
 From about 22 to 30 weeks, it begins to feed upon a substance called
"pap", which the mother produces in addition to milk.
 Milk feeding
 The Joey just lives near the teat and from there it starts sucking
mother’s milk.
 There the baby finds a nipple, which swells in its mouth keeping the
joey in place.
 After about 22 weeks, its eyes open and it begins to peep out of the
pouch. Moreover, the newborn Koala joeys’ sense of smell helps them
to identify the milk presence within the pouch of the female Koalas.

7. • Pap:
 After the joey spends 6 months in the pouch developing, the
mother koala will produce a special substance called pap.
 So the joey feeds on pap in addition to milk for several weeks
before leaving the pouch.
 Milk Composition
 Koala milk composition showed a number of deviations from the
general marsupial pattern that suggest koalas have adopted a
lactational strategy different from that of most other marsupials
previously studied.
 The carbohydrates of late-lactation koala milk contained mainly
lactose and some oligosaccharides, but little or none of the
monosaccharide found in the milk of many other marsupials.

8. • Joeys
 Like all marsupial babies, baby koalas are called joeys.
 A koala joey is the size of a jellybean!.
 The Koala joey is blind when it is born, and relies totally on its
well-developed senses of touch and smell and strong forelimbs
and claws to help it get to the pouch.
 Duration of lactation period:
 The young Koala only drinks its mother's milk for the first six to
seven months and remains in the pouch for that time, slowly
growing and developing eyes, ears and fur. At about 22 weeks, its
eyes open and it begins to peep out of the pouch. From about 22
to 30 weeks, it begins to feed upon a substance called "pap",
which the mother produces in addition to milk.

9. • Lactation in Kangaroos
 Lactation in kangaroos provides all the nutrients and energy for
growth and development during most of the pouch life, this being
about eight months duration in the red kangaroo, wallaroos and
euros and some ten months for grey kangaroos.
 Joeys are not weaned until four to eight months after leaving the
pouch.
 Again the relatively slower growth rate of the eastern grey
kangaroo is compensated for by the later weaning of the young.

10. • Kangaroo pregnancy
 After a gestation of up to 34 days, the jellybean-sized
baby kangaroo makes the journey from birth canal to pouch
by clambering up through its mother's fur
 Kangaroos and wallabies don't reproduce the way most of their
fellow mammals do, they keep their pregnancies short and to the
point, with young crawling out of the womb and up to their
mother's pouch after just a month's gestation.
 Marsupium
 Kangaroos and other marsupials have a special pouch called a
marsupium, for carrying their babies, because their young are
particularly small when they're born.

11. • Lactation: Essential for immunity
 Consumption of the milk is tailored to the requirements of the
developing young.
 An example is the increase in sulphur-containing amino acids
around the time of hair formation; hair has a high content of
sulphur containing proteins.
 Since milk is the only source of nutrients and micronutrients, e.g.
vitamins, it is presumed that their levels in the milk are adjusted
to meet the differing requirements of the young as it develops.
 Lactation Problem
 The most common cause of lactation failure is insufficient milk or
no milk (80%). The inflammation of mammary gland

12. Infraclass: Placental
 Placental mammals are the most diverse group of mammals with
about 4000 discovered species.
 Being the most diverse subclass of mammals, it includes dogs,
cats, rodents, elephants, whales, cattle, pigs, humans, etc.

13. • Lactation in House Mouse:
 The standard behavior of a lactating house mouse with 7–8 young can be
described as follows:
 During days 1–16 the offspring fully depend on the mother for nutrition.
 Due to rapid growth of the litter, the energetic demands of lactation reach a
peak for the female during days 13–16.
 During days 17–22, the weaning period, the young begin to eat solid food.
 Lactation in Cat
 Lactation, milk production is the secretion of milk through the mammary
gland to feed kitten.
 Cats are mammals, so called because they have mammary glands.
 Lactation is the most energy-consuming time in a cat’s life, and the queen
must eat a high-quality diet to provide enough calories to produce enough
milk for the kittens as well as maintain a healthy weight herself.

14. Contd…
 Once they give birth, the kittens will to receive the first milk that
the mother cat produces called colostrum. need
 This special milk has important nutrients in it that newborn
kittens need to properly grow and be healthy.
 During pregnancy, the cat's breasts are preparing for their future
milk production. These glands enlarge and, immediately after
giving birth, they begin to produce colostrum.
 The kittens will catch on with their mouths and, as they grow,
knead the breast with their paws.
.

15. • Lactation in humans
Mammary glands:
 Mammary glands are modified sweat glands.
 The non-pregnant and non-lactating female breast is composed
primarily of adipose and collagenous tissue, with mammary
glands making up a very minor proportion of breast volume.
Role of Hormones:
 During pregnancy the combination of estrogen and progesterone
circulating in the blood appears to inhibit milk secretion by
blocking the release of prolactin from the pituitary gland and by
making the mammary gland cells unresponsive to this pituitary
hormone

16. • The Role of Prolactin
 Human prolactin is a significant hormone in pregnancy and
lactation.
 Prolactin exists in both the male and the female of the species
and normal prolactin levels vary physiologically throughout life.
double the baseline.
 It has also been observed that the prolactin levels do not rise
unless the breast is stimulated either by the infant’s suckling or by
pumping even though the mother may be in contact with her
infant.

17. • The Role of Oxytocin
 Oxytocin is not just a female hormone.
 It is produced by both males and females and not just during
reproduction in the female.
 It is credited with producing increased responsiveness to
closeness, openness to relationships, and nurturing.
 The oxytocin circulating during breastfeeding has been credited
with producing calm, lack of stress, and an enhanced ability to
interact with the infant.

18. • Dietary Requirements
 Human lactation causes a major increase in the mother's
requirement for most nutrients.
 The lactating woman must meet the challenge of producing milk
adequate in volume and nutrient composition to meet the
requirements of her infant, while maintaining her own nutritional
status.
 This is mainly achieved by an increased maternal dietary intake
of energy and nutrients, otherwise nutrient depletion may occur
due to excessive mobilization of maternal stores.
 Recommended intakes of most nutrients for lactation are 10–90%
higher than for non-pregnant, non-lactating women.

19. • References
 F. A. E. Crew and L. Mirskaia. (14th March 1930). The lactation interval in the
mouse.
 Cindy Grigg, (11 may 2009) Article: Lactation in Three types of mammals.
 Katrina M.Moris, Denis O Meally, Thiri Zaw, Xiaomin,Amber Gillet,Mark P.
Molloy and Katherine Bolve, (2016) The Lactation in Marsupials.
 Acta Paediatrica, (1998), 87:440-445. 13 Cattaneo A, et al. Lactation method
in Kangaroo.
 Journal of Tropical Pediatrics, (1998), 44:279-282. 14 Bergman NJ, Jürisoo
LA. The “lactation-method in human beings” for treating low birth weight
babies in a developing country.
 Tropical Doctor, (1994), 24:57-60. 15 Lincetto O, Nazir AI, Cattaneo A. The
Lactation process in cat.