Physiology of Lactation

Suporn KatawatinDepartment of Animal Science

Khon Kaen University

Lactation?????

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Which of the following would you not expect to lactate?

Why milk?

It’s Mammal

Major characteristic of mammal

Lactation

as a critical part of their reproductive strategy

Outline

Evolution of mammary gland in mammals

Anatomy of mammary gland

Mammary Development

Evolution of Mammary Gland

Mammals

evolved from

mammal-like reptiles

210-220 million years ago,

before the first dinosaurs

Why evolve the ability, or

necessity, to lactate?

One theory

proto-mammalslaid soft-shelled eggs,

susceptible to bacterial or fungal infections

developed skin glands

secreted anti-microbial fluid to coat eggs

Monotremes: Duck-billed Platypus (Ornithorhynchus)

• egg laying mammals

• most primitive mammary glands

• do not have teats

• secreted to hairs, lapped by young

• no internal storage of milk

• young are born live

• mammary gland inside a "pouch"

• 4 teats, each teat is one gland

• no cistern (no milk storage)

Marsupials : Tammar Wallaby - a kangaroo (Macropus eugenii)

nonsuckledteats

newborn wallaby attached to teat

large teat

• nanny and ewe have two glands

• each drained by single teat with

single streak canal

• goat teats and udder are larger

• fine hairs on the teats

• blood and lymph systems similar

to cow's

Goats and Sheep

• 12-14 complex glands

• two parallel rows, ventral midline

• number on each side, even or odd

• secretory tissue independent from

adjacent gland

Pigs

• low heritability (0.1 - 0.2)

• little relationship with maternal performance

but gilts are chosen for breeding based partially

on number of teats

• Most breed associations require 12 functional

teats for pure bred registry

Pigs: teat number

CONCLUSION

Evolution of mammals

secretion is less like serum in composition

less taking pre-synthesized components

from blood

As gland becomes more specialized

Cows produce milk/year 10-20 X their wt.

whale mammary gland is 1.5 M long, 0.65 M deep, 0.2 M wide and weighs ~250 lbs.

young grow at 200 lbs/ day on 130 gal. milk,

40 feedings/ day

Males have rudimentary ducts and teats. EXCEPT - Male rats and mice have no teats.

Stallions have no mammary structures at all

Some facts about mammary gland & mammals

Mammary Gland and Mammals

great variability of external appearance of mammary glandsyield and composition of milk even within species

in contrast, internal structure of mammary tissue does not vary much for eutherian mammals

It is Skin Gland

Next topic isAnatomy of

Mammary gland