Lecture 8: Lacation Flashcards
what is puerperium
Period following parturition where the reproductive tract turns back to its non-pregnant state
During puerperium, myometrial contractions occur to do what?
Shrink the uterus (involution) and expel Lochia (blood, uterine lining, discharge)
What is the economic benefit of shortening the puerperium period in livestock
Increase frequency of breeding, increased pregnancy in dairy cows increases lifetime milk yield
What is the time required for uterine involution in a beef cow
30 days
What is the time required for resumption of ovarian activity in a beef cow
50-60 days
What is the time required for uterine involution in the bitch
90 days
What is the time required for resumption of ovarian activity in the bitch
150 days
What is the time required for uterine involution in the dairy cow
45-50 days
What is the time required for resumption of ovarian activity in the dairy cow
18-25 days
What is the time required for uterine involution in the mare
21-28 days
What is the time required for resumption of ovarian activity in the mare
5-12 days
What is the time required for uterine involution in the queen
30 days
What is the time required for resumption of ovarian activity in the queen
30 days
In dairy cows, calves are often removed within 24 hours, why?
Fewer oxytocin episodes that extend puerperium, avoids delayed involution that may delay reproduction
Is energy balance negative or positive in cows after parturition
Negative
To maximize milk production cows are usually bred at least every __ days
365 days
The first ovulation post partum occurs without any visible signs of estrus why?
Silent ovulations because have yet to produce progesterone and estrogen that will induce behavioral estrus
In some cows nursing may delay estrus, why?
Suckling feedback loop suppresses GnRH and LH therefore can’t induce estrus or ovulation
Describe changes from silent ovulation to first behavioral estrus
- After anestrus or pregnancy the ovary follicle develops without behavioral estrus (silent)
- CL produced from the ovulation follicle from silent ovulation secretes progesterone that “primes” the brain, no behavioral estrus
- Priming of the brain by progesterone enables estradiol secretion by next ovulatory follicle to elicit behavioral estrus
Mammary glands are ___glands
Sweat
What are mammary ridges
Occur as two lines of tissue that run centrally from the axial region to the inguinal region
What are primary mammary buds
Result of thickened epidermal tissue that penetrates into the dermis
What are secondary mammary buds
Occur as branching that further invades the dermis
What is canalization
Occurs when the duct system dorms with cells that have excretory capacity and myoepithelial cells that have contractile capability
At birth, mammary glands consist of ___ducts that open into a large canal that opens through teat or nipple
Lactiferous
What occurs during post natal growth of mammary glands
Isometric expansion in 1:1 ratio of mammary tissue with body growth, adds CT and fat
What occurs at puberty with mammary gland growth
Increased growth of fat and CT; expansion of lobular-alveolar growth of excretory tissue
What occurs at pregnancy with mammary gland growth
Further expansion of lobular alveolar growth of excretory tissue
Where do lobules empty into
Single milk duct
What are the milk secreting cells of the mammary gland
Parenchyma
What stimulates growth of mammary tissue during puberty
Estrogen, adrenal steroids, growth hormone
What stimulates early gestation growth of mammary tissue
Estrogen, progesterone, prolactin, growth hormone, adrenal steroids
What stimulates growth of mammary tissue late in gestation for milk secretion
Prolactin and adrenal steroids
Some species- cows and goats have ___that increase storage volume of the udder
Cisterns
Where is most milk stored in mammary tissue
Alveoli system
What is the mammary arrangement for the cow (location, # of teats, # of canals)
Quarters
Inguinal
4 teats
1 canal/cistern per teat
What is the mammary arrangement for the mare (location, # teats, # ducts)
Inguinal
2 teats
2 ducts per teat
What is the mammary arrangement for the bitch and queen (# teats, #ducts)
8 teats, 5-6 ducts/teat
What is lactogenesis
Series of cellular changes whereby mammary epithelial cells are converted from a non-secretory state ton a secretory state
When does lactogenesis begin in cows
4 days before parturition
What characterizes lactogenesis
Increase in lactose, total protein, immunoglobulins and decrease in sodium and chloride content
What are the two stages of lactogenesis
- Prenatal cytologic and enzymatic differentiation of alveolar epithelial cells driven by estrogen and prolactin
- Postnatal secretion of milk components. Sudden withdrawal of progesterone at birth causes blood flow to mammary glands to increase
What drives prenatal cytologic and enzymatic differentiation of alveolar epithelial cells
Estrogen and prolactin
What hormone decreases at birth causing blood flow to mammary glands to increase
Progesterone
What is galactopoeisis
Maintenance of lactation once lactation has been established, suckling initiates this series of events
What is involution
Return to non-secretory state
What two components contribute to the maintenance of lactation
Galactopoietic hormones and removal of accumulated milk
What is the first milk
Colostrum
What is colostrum rich in
Protein, fat, vit. A, Beta carotene, vit. E, thiamine, riboflavin
Colostrum has lower amounts of what
Lactose and pantothenic acid (vit. B5)
Colostrum provides ___immunity
Passive
Immunoglobulin absorption is limited to the first ___hrs of life
24-36
What hormone is important for the postresection adaptation response
IGF-1
What glycoprotein has strong anti-microbial activity
Lactoferrin
What causes the “cheese” color in colostrum
B-carotene
Cheese color is a result of
Nutrition and species differences of B-carotene in their milk
Yellow cheddar from what type of cows
Grass fed
White cheddar from what type of cows
Grain fed
White cheese is typically made from what animals due to lower ___
Sheep and goats due to lower carotenoids in milk
What is the main energy component in milk
Fat
What is required to breakdown Lactose
Lactase that converts it into glucose and galactose which are more absorbable
What are the building blocks of milk synthesis
Fats, proteins, and lactose
What are fats involved in milk synthesis composed of
Mono, di-triglycerides, FFA, phospholipids, steroids
Where does fat accumulate in mammary tissue
Basal cytoplasm
Where does fat move in the mammary tissue for milk synthesis
Apex where the droplet protrudes in alveolar lumen
How is the fat droplet dispersed in mammary tissue
Cell membrane constricts about the base of the gat droplet to disperse the milk in small droplets surrounded by the cell membrane
What are proteins involved in milk synthesis composed of
Casein, albumins, globulins
Where are milk proteins synthesized
Endoplasmic reticulum of alveolar cells
Where do casein molecules pass to in milk synthesis
Golgi apparatus
How is casein released
Golgi vesicles fuse with cell membranes are are exocytosed
What is lactose composed of
Disaccharide of galactose and glucose
Glucose is converted to ___ in milk synthesis
Galactose
Galactose is actively transported into __ during milk synthesis
Golgi lumen
How does glucose pass across Golgi membrane into lumen
GLUT1
What enzyme facilitates lactose synthase reaction
Lactose synthase
What hormones immediately decline with birth of placenta
Estrogen and progesterone
What hormone plays a role in milk synthesis and is activated immediately after birth of placenta
Prolactin
What hormone is responsible for the inhibition of prolactin secretion
Dopamine
What does suckling by the infant stimulate
Mechanoreceptors that synapse with neural circuits by two types of neurons excretory cells
- inhibit dopamine
- stimulate vasoactive intestinal peptide
- release prolactin
Describe the steps/role of oxytocin in milk let down
- Suckling activates mechanoreceptors
- PVN releases oxytocin via posterior pituitary into blood
- Myoepithelial cells contract, OT causes contraction and moves milk into ducts and cistern
- Milk let down results
What hormone acts to release milk
Oxytocin
Describe the difference between oxytocin vs prolactin
Prolactin is responsible for milk synthesis/production
Oxytocin is responsible for contraction and milk let down
How does neonates crying or smell impact oxytocin and prolactin
Increase
How does psychological stress impact oxytocin and prolactin
Decrease
What is milk fever
Result of high demand of Ca2+ in colostrum which results in hypocalcemia, reduced activity, depression, paralysis
What is secreted in response to low blood serum calcium
PTH
How does PTH hormone work to increase Ca2+ levels
Stimulates bone resorption
What is the problem with PTH in milk fever
Slow
Continuous milking maintains ___
Galactopoesis therefore increases milk production
What is the result of insufficient removal of milk
Pressure atrophy, pressure on alveolar milk secreting cells inhibits galactopoesis resulting in involution
What is active involution
1-2 days of increased pressure inhibits milk secretion, prolactin release still response to feedback
What is steady state involution
Sustained period of inhibited milk synthesis that lasts until next birth, prolactin release is blocked
Milk synthesis can be halted in ___days with loss of nursing
1-2 days
What is mastitis
Inflammation of udder and mammary gland in response to infection with bacteria, fungi, mycoplasma, algae
How is mastitis transmitted
Contact with milking machine, dirty hands, bedding, insects
What does mastitis lead to
Formation of non-functional CT in order to wall off infection
When are/what time fram are cows at greatest risk of mastitis
Active involution and colostrogenesis
