Lactation Flashcards
When does mammary gland development begin?
Whilst the foetus is in utero - teats can be seen on an ultrasound
What is the predominant dairy breed?
Holstein
How how the dairy herd yield been increased progressively despite the number of farms decreasing?
- Improved genetics (AI)
- Improved nutrition
- Improved technology
Why had yield advanced the most amongst dairy breeds?
It has the highest heritability
What are some of the main problems associated with lactation?
- Decreased fertility
- Compromised immune function
- Increased lameness
- Mastitis
- Metabolic stress
What are the 3 major components of all milks?
Protein
Fat
Lactose
What are the major proteins of milk and where are they found?
Caseins - found in the curd
For how many days is milk withheld for human consumption following parturition?
4
Colostrum provides what type of immunity?
Passive
What are the components of colostrum?
- high in fats, protein, and vitamin A
- low in lactose
Describe the embryology of mammary glands
- Two parallel lines of ventro-lateral ectoderm in the embryo
- Develop into thickenings known as mammary band
- Mammary buds grow into underlying mesenchyme
- Mammary glands = epithelial
What occurs following the removal of a wrong supernumerary teat?
1/4 of the udder won’t be able to release milk
What anatomy makes up the mammary gland?
- Teat/nipple and associated ducts
- Alveoli, secretory cells and supporting tissues
Which structure separates the gland cistern from the teat cistern?
Annular fold
Which ligaments form the suspensory system attaching the udder to the body?
- Median suspensory ligament
- Pre-pubic and sub-pubic ligaments
Describe the structure of the gland
- secretory tissue (parenchyma)
- ducts
- storage sinus (cistern) lying in a fat pad
- terminating externally in a teat or nipple
What is the function of the cistern between the teat and udder?
Large cavity where milk can collect between milking
Despite the presence of large cisterns, where is most of the milk actually stored?
Alveoli
The alveolus is a basket like arrangement of what type of cells?
Polarized epithelial secretory cells
What surrounds the polarized epithelial secretory cells in the alveolus?
Myoepithelial (smooth muscle) cells and blood vessels
The number of secretory cells is a prime determinant of what?
Milk yield
Until puberty mammary tissue grows at what rate?
Same as the rest of the body - isometric growth
Following puberty/oestrus cycle, at what rate does mammary tissue grow at?
Faster than the rest of the body - Allometric
How do mammary cells change from gestation to the end of lactation?
- Secretory cells proliferate during gestation
- Some proliferation in early lactation, but mainly differentiation
- Gradual involution (apoptosis) during declining lactation
- Rapid involution after drying off or weaning
Which hormones cause growth of ducts?
Oestrogen + growth hormone + adrenal steroid
Which hormones cause milk secretion?
Prolactin + adrenal steroids
Describe stage 1 and 2 of lactogenesis
- Acquisition of secretory capability pre-partum
2. Onset of copious secretion at around parturition
What is the main hormonal requirement for the onset of lactogenesis?
Progesterone withdrawal
How does the foetus syncronise stage 2 of lactogenesis with parturition/milk production?
- The foetus signals from its own hypothalamus and pituitary to secrete cortisol from the adrenal gland
- This passes across the placenta and increases oestrogen levels
- This stimulates PGF2a release from the uterus
- This goes to the ovaries causing luteolysis of the CL, and a decline of progesterone
- This stimulates labour and production of milk
Teat stimulation evokes which reflex?
Neuroendocrine reflex - develops positive pressure in the udder
Describe the milk-ejection reflex
- Teat stimulation causes afferent inputs to go to the hypothalamus
- Causes oxytocin to be released from the posterior pituitary
- Leading to contraction of myoepithelial cells in the mammary gland
Describe a milking routine
- Clean teat (pre-dip or wipe)
- Inspect for clots - foremilk
- Leave for 30 seconds to allow for oxytocin action
- Cluster on
- Milk flow reduced
- Cluster off
- Post milking teat dip applied
What is galactopoiesis?
Maintenance of established lactation
Continued milking does 2 things, what are they?
- Stimulates the release of galactopoietic hormones
- Prevents milk stasis
How is the drive for lactation different in cows to most species?
- In cows it is GnRH driven
- In most other species it is prolactin driven
What is BTS and why is it now banned in the EU?
- Method that significantly increased milk yield of dairy cows
- But had serious consequence on health and welfare
What 3 things inhibit apoptosis?
- Prolactin
- GH
- IGF1
What 2 things stimulate apoptosis?
- Weaning
- Milk stasis
How long is the optimal dry period?
60 days
