Lactation Flashcards
During foetal development and pregnancy, what happens to the dam?
Mammogenesis
Before, during and after parturition, what takes place?
Lactogenesis
After parturition an during neonatal development, what takes place?
Galactopoiesis
What is the predominant dairy herd (UK)? What is the UK average yield?
Holstein
What is the average milk composition (fat, protein and lactose)
4% fat
- 2% protein
- 5% lactose
How has milk yield increased over the decades
Improved genetics (AI)
Improved nutrition
Improved technology
What problems are associated with lactation? (most problems are early lactation)
Decreased fertility Metabolic stress Compromised immune function Mastitis Increased lameness
What is the majority of milk proteins?
Caseins
Apart from caseins, whey proteins are also in milk. What do they include?
B lactoglobulin
A lactalbumin
Immunoglobulins
Why might variation in milk composition occur?
Between breeds Between species Across lactation and milking Nutrition With seasons
How is colostrum formed?
Pre-partum milk secretions that is not removed –> colostrum
Does colostrum provide passive or active immunity? Where are the immunoglobulins produced?
Passive
By plasma cells in the mammary gland
Describe the composition of colostrum in terms of fat, proteins, vitamins and lactose
High fat
High protein
High vit A
Low lactose
How long is colostrum secreted for? How long is milk withheld from human consumption?
Several days
4 days
Mammary glands form from which germ layers?
Ectoderm
Develop into mammary band
Mammary buds grow into underlying mesenchyme
What type of glands are mammary glands (simple, compound, alveolar, tubular, alveolar)?
Compound alveolar
What is the name of extra mammary buds formed during development? (Often removed in dairy heifers)
Supranumery teats
What separates the teat cistern from the glandular cistern?
Annular fold
What is present around the teat (streak canal)?
Sphincter muscle
What attaches the udder to the body? What does this consist of?
Suspensory system (4 ligaments): Median, lateral, pre- pubic and sub-pubic ligaments
The gross anatomy of the udder is separated into…
Rear and fore quarters (attached to body via rear/fore quarter attachment)
Mammary groove running between L and R teats
What is the name of the secretory tissue in mammary glands?
Parenchyma
What is the name of the ducts and storage sinus within a fat pad of the udder? What happens here?
Cistern
udder cistern and teat cistern
Ducts move milk from where to where?
Alveoli to teat
No internal crossover
Where is miked stored between milking?
Some in cisterns
Most in alveoli
How does the teat canal respond to infection?
Cytokine production
The alveoli consists of what cell arrangement?
Polarised, epithelial secretory cells
What surrounds the alveoli?
Myoepithelial cells (smooth muscle) Blood vessels
How is milk ejected from alveoli into ducts?
Contraction of myoepithelial cells
What are the secretory cells? From which surface is milk synthesised?
Cells on basement membrane surrounded by collagenous extracellular matrix
Apical surface
What is the prime determinant of milk yield?
Number of secretory cells
What happens to the cells in the udder during pregnancy and early lactation?
Proliferation of secretory cells displace fat pads
Mainly differentiation in early lactation
Describe growth of the mammary tissue during puberty and during oestrus cycles
Puberty = isometric growth (grows in proportion to rest of body)
Oestrus cycle = allometric growth (grows at different rate to rest of organs) and regression
What happens to the cells of the udder during declining lactation?
Apoptosis
And involution
Which hormones cause duct growth?
Oestrogen
Growth hormone
Adrenal steroids
Which hormones cause lobulo-alveolar growth?
Oestrogen Growth hormone Adrenal steroids Prolactin Progesterone
Which hormones cause milk secretion?
Prolactin
Adrenal steroids
What are the phases that take place to cause milk secretion?
Atrophic ducts
Duct growth
Lobulo-alveolar growth
Milk secretion
Which hormones are important in the control go bovine mammary cell proliferation?
Placental lactose
Growth hormone
(NOT PROLACTIN)
What are the 2 stages of lactogenesis?
Acquisition of secretory capability pre-partum
Onset of copious secretion at parturition
What hormone is the main requirement for lactogenesis?
Progesterone withdrawal
How is milk ejected from the gland?
Teat stimulation causes neuro-endocrine reflex
Oxytocin released from posterior pituitary
Myoepithelial cells in mammary gland contract
Positive pressure in the udder causes milk to be pushed out
Describe a basic milking routine
Clean (predip/wipe) udders
Identify animal
Inspect for clots
Leave 30-45 seconds for oxytocin release and action
Cluster on then removed
Teat dip applied post milking
Loafing time to allow teat sphincter to close
What is galactopoeisis?
Maintenance of established lactation
What does continued milking do to allow galactopoiesis?
Prevents milk stasis
Stimulates the release of galactopoiesis hormones
How does milk stasis inhibit milk secretion? (2 ways)
Feedback inhibition (within hours) Physical disruption (within days)
In most species, what hormone drives lactation? Which species is the exception and what hormone drives their lactation?
Most species = prolactin
Cows = growth hormone
A 3 quarted cow reduces yield by what percentage?
10% (not 25%)
How can milking yield be increased?
Recombinant bovine somatotropin (rBST)
Genetic improvement
Nutrition
Frequent milking
Is BST legal in the EU? Why?
No
Burnt out after one lactation and replaced
Causes lameness and painful injection abscesses
How does bovine somatotropin cause an increased milk yield?
Redirects nutrients towards the other
Give one way that milk production can be inhibited to match supply to demand
Feedback inhibitor of lactation (FIL - autocrine peptide)
Negative feedback
Large cistern cows produce more milk per gram of secretory tissue. Do large cistern cows tolerate frequent or infrequent milking better?
Tolerate infrequent milking
Respond less well to frequent milking
After peak lactation, what causes milk yield to decrease?
Decreased number of secretory cells by apoptosis
Due to FIL and lack of gelactopoietic hormones
What stimulates apoptosis of secretory cells?
Weaning
Milk stasis
Local increase in IGFBP5
What inhibits apoptosis in secretory cells?
Prolactin
Growth hormone
IGF1
What are the types of milking parlour?
Abreast Tandem Herring bone Rapid exit Rotary Robot
How milking clusters cause milking?
Vacuum creates negative pressure outside the teat
Pushes milk out
Vacuum on:off 2:2
