Lactation

List milk composition

normally:

• 4.5% lactulose

• 4% fat

• 3.2% protein

What are some non-nutritional influences on composition and milk yield

Frequency of milking

• more milking = longer production therefore increased yield.

Describe gross udder anatomy

Rear and Fore quarters. Mammary groove down middline.

Describe internal udder anatomy

Alveoli lying on basement membrane, surrounded by smooth muscle.

Myoepithelial cells eject milk into ducts

Ducts move milk from alveoli to teats, udder cistern stored milk and opens into teat cistern (sphincter muscle contracts, annular fold separates.

Describe the suspensor system in udders.

Contains the median suspensory ligament, pre-pubic and sub-pubic ligaments

Describe mammogenesis

Isometric growth until puberty.

Puberty

• oestrogen, duct branching + widening

• progesterone - alveoli formation at terminal portions

• prolactin + GH - rapid development of ducts

Gestation needed to complete development.

Explain the physiological control of mammogenesis

During puberty:

• oestrogen, duct branching + widening

• progesterone - alveoli formation at terminal portions

• prolactin + GH - rapid development of ducts

Gestation = completed development

Describe allometric growth + regression during oestrus cycle

• initially - extensive duct system lying in fat pad

• during gestation - secretory cells proliferate (displace fat)

• during lactation - mainly differentiation

• drying-off - gradual apoptosis

• after drying off - rapid apoptosis

Explain the physiological control of lactogenesis (2 stages)

• stage 1 - acquisition of secretory capability pre-partum

• stage 2 - onset of secretion at parturition

  • systemic endocrine control - progesterone withdrawal

  • local control

Explain the physiological control of galactopoiesis

= maintenance of established lactation

local = IGF-1

systematic = GH and prolactin

prevents milk stasis

Explain the physiological control of apoptosis

after peak lactation

• cell no and yield decline together

after cessation of suckling

• rapid increase

gland returns to less developed state

controlled by prolactin, GH, IGF-1.

stimulated by weaning, milk stasis, IGFBP5

Describe mechanisms of milk let down

Teat stimulation → neuro-endocrine reflex

• positive pressure in udder

• bulk of milk obtained

• stimulated by machine

How does milk let down influence milking routine

• clean - pre-dip

  • identify animal

  • foremilk - inspect for clots

  • leave 30-45 seconds - oxytocin + pre-dip action

• wipe off pre-dip

• cluster on

• milk flow reduced → cluster off

  • post-milking teat dip

  • loafing time - teat dip action + teat closure

Name 5 milking systems

Herringbone

• 50 or 30 degrees through the legs

Tandem

• 2 rows of 2 cows

Rapid exit

• long line, fast release

Rotatory

• cows on floating rotating thing, staff standing still

Automated

• cows choice?