Lecture 13 - Lactation pt 1 Flashcards
Why can’t we feed swine milk from bovines?
- milk composition is species specific
- would be short on how much fat (energy) they are getting
What 2 monosaccharides join to make lactose?
galactose + glucose
What is ash?
- close to 1% of milk
- iron, magnesium, iron, phosphorus
How is the mammary gland structure species specific?
- location
- number of glands
- largely associated to how many offspring they have - number of cisterns
- number of teat canals
What is the mammary gland structure of the udder?
- 4 separate glands
- one teat in each quarter
What are supernumerary teats?
- extra nonfunctional teats
- get removed when calf is young
What are key aspects of good conformation of teats?
- moderate size
- central in each quarter
- tight sphincter
What are the 3 major supporting structures of the mammary gland?
- skin
- median suspensory ligament
- lateral suspensory ligament
Median suspensory ligament
- supporting structure of the mammary gland
- separates right and left halves of udder
- connects udder to abdominal wall
- elastic tissue which responds to wt of milk in udder
Lateral suspensory ligament
- inflexible
- surrounds the outer wall of the udder
- attached to prepubic and subpubic tendons
Intermammary groove
- left x right halves
- where median and lateral suspensory ligaments meet
- indicates the cow has good attachment; well attached udder fits snugly against the abdominal wall in front and on the sides
Characteristics of a good, non-lactating udder?
- fully collapsed
- firm attachment
- uniform teats
Characteristics of a good, lactating udder?
- strongly attached
- teat size and shape
- udder size
Abnormalities of a bad udder
- attachment failure
- udder size and shape
- teat size, shape, and placement
What is the alveolus?
- functional, milk production unit
- bulb shaped
- hollow center
- lined with epithelial cells
What is the fxn of epithelial cells of the alveoli?
- milk synthesis and secretion
What is the fxn of the lumen of alveoli?
- collect milk components and water
What is the fxn of myoepithelial cells of alveoli?
- milk ejection
- contract in response to oxytocin
What is the fxn of the basement membrane of alveoli?
- separates epithelial and myoepithelial cells
What is the fxn of the terminal duct of alveoli?
- milk transport out of alveoli
What is the fxn of the capillary system of alveoli?
- support milk precursors, deliver hormones, support blood supply
Alveoli duct system
- storage and transport
- 2 layers of epithelium
- myoepithelial cells arranged in a longitudinal pattern; contraction = milk flow
Furstenburg’s rosette
contributes to immune cell population
What does the streak canal do?
- keeps milk in (tight) and bacteria out
What are the 4 development processes of mammary tissue?
- mammogenesis
- tissue growth and development - lactogenesis
- differentiation of alveolar cells into milk producing and secreting cells - galactogenesis
- maintencance/enhancement of lactation - involution
- when cow is no longer lactating, the tissue that has been built needs to all go away
What is happening to the mammary gland from birth to puberty?
- isometic growth = mammary growing at same rate as the rest of the body
- hormones impacting growth
What is happening to the mammary gland from puberty to conception?
- allometric growth starts before first estrus = mammary growing faster than the body
- induced by estrogen - estrogen (ovary)
- branching/elongation of ductal system
- increased vascularity - prolactin and somatotropin
- contribute to overall growth
What is happening to the mammary gland from conception to parturition?
- allometric growth
- exponential parenchyma proliferation
- early: branching/elongation of ductal system
- late: alveolar development
- hormones contributing to growth
- insulin + IGF-1
- thyroid hormones increase metabolic rate
Lactogenesis
Late gestation
- high P4; stops lactation from happening
- block prolactin receptor synthesis
Parturition
- P4 falls
- prolactin receptors synthesized
Prolactin stimulates synthesis of alpha-lactalbumin initiating secretion of milk
Milk ejection reflex aka how is milk secreted?
- oxytocin and prolactin released from pituitary following stimulation of skin on teats (or sight/smell/sounds of calf)
- Oxytocin has 3 stimulatory effects on the udder
1. increases pressure in alveolar lumen; myoepithelial cells contract
2. reduces resistance in small excretory ducts
3. reduces resistance in teat canal
Factors affecting emptying of the udder
Activation of sympathetic nervous system inhibits milk let-down by:
- reducing secretion of oxytocin
- inhibiting the response of myoepithelial cells to oxytocin
- eliciting contraction of the smooth m cells in the sphincter at the top of the teat
- reducing blood flow to udder
What can larger residual milk volume in the udder lead to? aka what is a concern by the sympathetic nervous system being activated and inhibiting milk let-down?
reduced production and increased risk of infection
What are 3 controls of milk secretion?
- physical control
- removal rate
- gland storage capacity
- intramammary pressure - chemical control
- feedback inhibitor of lactation- slows milk secretion; produced in response to increased pressure - after milking
- prolactin release is stimulated
- decrease in intramammary hydrostatic pressure
- FIL is removed from alveoli
Involution/Dry-period
- when we stop milking we are going to have involution where the tissue degrades back to a prelactation form
- feedback inhibitor of lactation (FIL) produced in mammary in response to pressure in alveoli
- alveoli shrink down and lose secretory capacity but are maintained for when she is pregnant; if waiting long enough they degrade
How much blood does one gallon of milk require?
- one gallon of milk requires 400 gallons of blood being passed through the udder
- ratio may increase in low producing cows
Path of blood to the mammary arteries
- heart
- caudal aorta
- iliac arteries
- external pudic arteries
- mammary arteries
How is milk returned to the heart from the mammary veins?
- mammary veins, external pudic vein, iliac veins, caudal vena cava, heart
- mammary veins, subcutaneous abdominal vein (milk vein), cranial vena cava, heart
6 characteristics of lymph (which is also going to the mammary)
- less protein than blood plasma
- high concentration of lymphocytes (aka immune cells)
- few RBC’s
- carries glucose, salts, fat
- dissipates heat
- carrier of fibrinogen (clotting protein)
How can the movement of lymph be described?
Passive
- muscle movement
- breathing
- heart beat
- tissue massage
What are the 4 main fxns of the lymphatic system?
- helps regulate proper fluid balance within the udder
- immune fxn (lymphocytes
- fluid drained from tissue only travels away from udder
- lymph travels from udder to the thoracic duct and empties into blood system
Edema
- accumulation of interstitial fluid
- lymphatic: low pressure, passive system
- circulatory system: high pressure, active system
= pooling of interstitial fluid if evacuation of lymph is impaired
What 5 things can prevent edema?
- preparturient milking
- frequent milking to reduce mammary pressure
- diuretics, corticoids to reduce swelling
- mammary massage, icing
- work fluid towards supramammary lymph nodes - reduce salt intake
