ovulation, lactation and milk productionadvis/300_phys_pdfs/300_35_amilkproduction...1 ovulation,...

1

Ovulation, Lactation

and Milk Production 35 The goal of this lecture is to discuss basic

physiology associated with the control of ovulation, lactation and milk production.The sections for this lecture are:

Life is a series of chemical reactions occurring in compartmentalized environments. The main purpose of life is to keep itself alive

Physiology, the study of how life works, is based on the simultaneous occurrence of the following three concepts:

levels of organizationstructure / function relationshiphomeostatic regulation

Hormonal profiles on ovulation, parturition and lactation

Physiological changes at parturition & their links to metabolic disorders in dairy cows

Thermoregulatory response jn young, calves response to heat in a hutch environment

Thermoregulatory response in adults, the fescue endophyte story in cows and the ergot toxicity in humans

Milk and egg production and Ca regulation

Ovulation, Parturition,

Lactation & Milk Production Role of gonadal steroids and others on ovulation, parturition and lactation

Physiological changes at parturition and their link to metabolic disorders

Thermoregulatory response of calves to heat in a hutch environment

The fescue Endophyte story in cows and that of Ergot toxicity in humans

Milk production and Ca regulation Adaptation to lactation diet, elimination of hypo-calcemia, and immunomodulation to stimulate immune system at birth would reduce incidence of periparturient diseases in humans and cows.

2






Milk production and Ca regulation Ruminal adaptation to lactation diet, elimination of hypoCa, and immunomodulation to stimulate immune system at calving would greatly reduce incidence of periparturient diseases in dary cows

Most metabolic diseases of dairy cows occur within the first two weeks of lactation. Others like laminitis can be traced back to that period

Role of gonadal steroids and others on ovulation, parturition and lactation




Milk production and Ca regulation

Ruminal adaptation to lactation diet, elimination of hypoCa, and immunomodulation to stimulate immune system at calving would greatly reduce incidence of periparturient diseases in dary cows


Lactation & Milk Production

3







E2 and P4 act in synchrony so that E2 promotes growth and P4 differentiation of their target tissues. E2 and P4 are steroids.

(E2)








(E2)

(P4)

4

Ovulation and Cyclicity





Milk production and Ca regulation The general pattern for the hormonal control of reproduction. Ovulation is triggered by estradiol induction of the preovulatory surge of LH, an obligatory event for reproduction to occur.


Parturition and its Control





Milk production and Ca regulation The general pattern for the hormonal control of reproduction. Ovulation is triggered by estradiol induction of the preovulatory surge of LH, an obligatory event for reproduction to occur.


5






Milk production and Ca regulation Parturition is associated with a decrease in blood Progesterone (P4) and an increase in blood Estradiol (E2). These combination depolarize the membrane potential of myometrial cells making them more suceptible to oxytocin & prostaglandins.


P4

E2








Parturition is associated with a decrease in blood Progesterone (P4) and an increase in blood Estradiol (E2). These combination depolarize the membrane potential of myometrial cells making them more suceptible to oxytocin & prostaglandins.

6

triggersonset ofparturition

mantainsparturition








Lactation and its Control





Milk production and Ca regulation Milk production results from the interaction of multiple metabolic hormonal systems on the mammary gland: hormones such as insulin, IGFs, GH, TSH, PRL, cortisol and aldosterone.


GH

E2P4InsulinIGFsTSHPRLCortisolAldosterone

7








GH








8








Suckling

Mechanoreceptors in nipple

Nervous pathway PIH orPRH (?)

Hypothalamus

Posterior pituitary Anterior pituitary

Prolactin Oxytocin

Milk secretion Myoepithelial cells

Milk ejection

+

Milk ejection results from binding oxytocin to its receptor on myoepithelial alveolar cells. Neuron linked “stress” related inputs to PVN and SON (oxytocin cell bodies loci) are also involved.

Periparturient Diseases






immunefunctionat parturition

DMIat parturition

E2 and P4at parturition

cortisolat parturition

stressat parturition

immunesuppressionat parturition

Ruminal adaptation to lactation diet, elimination of hypoCa, and immunomodulation to stimulate immune system at calving would greatly reduce incidence of periparturient diseases in dary cows

How do we know that this THM is correct

9









DMIat parturition













DMIat parturition





10









DMIat parturition





P4

E2









DMIat parturition





Cows that

developed

hypocalcemia

and milk fever

Cows

that

did

not

11









DMIat parturition













DMIat parturition





12









DMIat parturition













DMIat parturition





13

Thermoregulatory Control






effect onthermo-regulationby a minimalchange inenvironmentaltemperatureassociated with the useof shadeshows thesensitivityof the thermo-regulatorycontrolsystem

Supplemental shade lowers severity of heat stress, in calves housed in hutches in summer, as assessed by body t°C and respiratory rate, after minimal increases in environmental t°CHow do we know that this THM is correct









14

















15







effect onthermo-regulationby ingestion of a grass containingendophytesand summerhigh t°C,shows howthe thermo-regulatorycontrolsystem can be modulated

Losses in cow-calf productivity due to fescue toxicosity are significant. Endophyte ingestion interacts with high t°C to exacerbate the signs of toxicosis. Low PRL and melatonin secretion appears to be associated with the disease.











16



















Points of discussion related to t°C regulation and to reproduction associated with the fescue story

Reduced PRL & melatonin secretionAltered NT metabolism in H, Pit, Pin

Lowers feed intake (22%, 32 vs 22°C)Increase water intake (62%, 32 vs 22)

Decreased calving and growth rateDelayed onset of pubertyImpaired function of corpora luteaDecreased reproductive efficiencyReduced weight gainsLower milk production

Based on data explored in the course, how would you explain results reported in the J. of Animal Science listed above

17








Ergocryptine is a dopamine receptor agonist used to inhibit Prolactin secretion in humans.

Ergot: Claviceps purpurea, a parasitic fungus on spoiled rye and other grains.

Its components and their derivatives include lysergic acid, lysergic acid amides, ergotamine,,ergocornine, ergocryptine, ergonovine, trimethylamine, histamine and acetylcholine,

The most common early effects of ingesting the grains are nausea, vomiting, diarrhea, tachycardia, abdominal pain, and coma..

Based on data explored in the course, how would you explain results related toErgot toxicity in humans

Ca, Milk and Egg Production






milk and egg productionare linked bythe control ofCa metabolism.Thus the role of PTH, VitDand calcitoninare importantto understandmanagement techniquesused in bothIndustries, as well as in human lactation.

Adequate blood calcium (Ca) and phosporus (P) concentrations are vital to normal animal function. Homeostatic mechanisms normally achieved this. Ca & P are key minerals in bone development in humans and cows, and egg formation in chickens.

18








Adequate blood calcium (Ca) and phosporous (P) concentrations are vital to normal animal function. Homeostatic mechanisms normally achieved this. Ca & P are key minerals in bone development in humans and cows, and egg formation in chickens.

Disorders of Ca metabolism may arise from abnormal levels of PTH or vitD.

Possible consequences of hypercalcemia and hypophosphatemia

Reduced excitability of muscle and nerve tissue leads to muscle weakness and neurological disorders. Cardiac disorders might also occur.

Excess mobilization of Ca and PO4 from bone leads to osteoporosis.

An increased incidence of Ca containing kidney stones occurs because the excess quantity of Ca being filtered may precipitate and form stones.









The Ca content of human milk is about 36 mg per 100

ml. A lactating woman produces about 750 ml of milk

daily, which represents about 280 mg of Ca.

For a maternal urinary Ca of 100 mg/day and skin loss

of 60 mg/day, the required absorption is 440 mg/day -

the same as at puberty.

However, although it is known that bone is lost during

lactation & restored after weaning, early reports that

this bone loss could be prevented by Ca supplemen-

tation have not been confirmed in controlled studies.

19









There are 9grs of Ca in ECF and 3grs in plasma. Daily output of Ca in milk is about 25grs.Lactating cows prevent hypocalcemia by taking Ca from bone or by increasing GI-Ca absorption.Bone Ca mobilization is regulated by PTH. VitD is needed to efficiently absorbed dietary Ca.Hypocalcemia and milk fever occur when cattle do not remove enough Ca from their bones and the diet to replace the Ca lost in the milk.









10% of total body Ca is secreted into shell, daily.Egg shell is made of calcium carbonate.PTH mobilize bone Ca when Ca deposition in the shell exceeds Ca absorbed by intestines.Reciprocal relation of PTH and Ca during the egg cycle.Ca transporters in laying birds shell gland is controlled by estrogen.

20








There are three tissue target in Ca metabolism that control blood levels of Ca: bones, kidneys and gut. PTH acts on bone and kidneys, vitD acts on the gut, and calcitonin in all three of them.








blood

Ca bone

kidney

intestine

resorption

formation

reabsorptionfiltration

secretion

absorptionPTH and Vit.D

increase bloodCa

while

Calcitonin

decreases it

PTH

Calcitonin

PTH

Calcitonin

Vit. D

calcium receptor

parathyroid gland

PTH

PTH receptorGs / AC

Gq / PLC

bone resorption, osteoclast

kidney, Ca reabsorption, Vit. D

intestine, Ca absorption

Calcitonin

thyroid gland

calcium

receptor

Calcitonin

receptor

Gs / AC

bone formation, osteoblast

kidney, Ca filtration

intestine, Ca secretion

blood Ca

decrease

blood Caincreas

e


21

















22

















23

















ç

24









irradiation

7-Dehydro

cholesterol

(pro Vit. D)

Cholecalci-

ferol

(Vit.

D3)

25-Hydroxy

cholecalciferol

(25 - (OH) - D3)

1, 25 -

Dihydroxy

cholecalci-

ferol

( 1, 25 -

(OH)2

D3 )

24, 25 - Dihydroxy

cholecalciferol

( 24, 25 - (OH)2 D3 )

25 -

hydroxy-

lation1 -

hydroxy

- latio

n

24 -

hydroxy-

lation

kidney

liver

skin

-

PTH

Low PO4

Low Ca

Estrogen

Prolactin

GH

Placental

lactogen

+









ovulation, lactation and milk productionadvis/300_phys_pdfs/300_35_amilkproduction...1 ovulation,...

Documents