Bovine reproduction Flashcards by Megan Palmisano

tubular components of female repro system

vulva/vagina, cervix, uterus, oviduct

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female gonads

ovaries

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broad ligament

fold of the peritoneum

mesometrium (between cervix and uterus)
mesosalpinx (oviduct)
mesovarium (ovaries)

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cow anatomy

large broad ligament
rectogenital pouch

internal bifurcation of the uterine horn

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female anatomy

ampulla= where fertilization takes place

sperm needs to reach tuba uterine junction

fimbrae connects to egg, ovarian bursa covers the ovary

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estrous cycle

period of reproductive cyclicality, which only ceases during pregnancy (cows not seasonal)

follicular and luteal phases

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phases of cycle

metestrus-CH (corpus hemoragicum)
diestrus- CL, progesterone, follicular wave (if not pregnant prostaglandin produced so CL lysed)
proestrus- CL, regression, final follicular maturation
estrus- PGF2a

within follicle have thecal cells (small luteal cells) and granulosa cells (large luteal cells)

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days of the estrous cycle

metestrus= lots of immature follicles (until day 5) 
diestrus= 2nd wave of follicular development (until day 15) 
proestrus= 3rd wave of follicular development- dominant follicle= ovulation

if no dominant follicle released during estrus (day 20-22) then luteolysis occurs in that same interval (decreased P4)

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cow estrous cycle

21 days, follicle selection= on going
all follicles produce estradiol and inhibin more dominant follicle produces more but also learns to grow under low FSH

progesterone decreases so can continue to grow and produce estradiol to induce ovulation

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atretic follicles

die with high progesterone

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follicular growth

dominant follicle removed so smaller follicles can grow

inhibin inhibits growth of other follicles

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surge center

induce ovulation

acts with tonic center to secrete GnRH

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tonic center

constant release of LH and FSH

growth and maintenance of the follicles

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GnRH

without GnRH no LH and FSH so no ovulation

LH induces ovulation

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Corpus luteum (ovary)

CL produces progesterone which prevents LH surge and pulsatile ability of LH

progesterone= - feedback on LH through surge and tonic center
low GnRH from hypothalamus to decrease LH

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Follicle and Ovary hormones

inhibin inhibits FSH so other follicular growth inhibited

position of dominance produce estradiol and increase FSH so other non dominant follicles atretic

LH and FSH from ant. pituitary act on follicle which results in negative feedback via inhibin on FSH
follicle releases E2 which will cause negative feedback on FSH and + feedback on surge center

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follicular phase of estrus cycle

proestrus and estrus

P4 decreases after diestrus (without decrease effect of LH)
proestrus- E2 increasing, peaks at estrus
estrus- LH surge, during surge progesterone at basal level and estradiol reaches threshold causing LH and FSH surge
P4 rises during metestrus

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ovulation

at end of follicular phase (estrus)

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Process of ovulation (hormones)

decrease P4 from CL, increases GnRH, increases FSH and LH, and proestrual follicular development

proestrual follicular development leads to increase inhibin which decreases FSH
also will increase estradiol to threshold which causes preovulatory LH surge

select only 1 follicle to develop because learn to not depend on FSH

luteolysis

cow, ewe, and goat: luteolysis is dependent on presence of the uterus; not in primates

a local effect in ruminants (uterine horn and ipsilateral ovary)

PGF2a enters ovarian artery from utero-ovarian vein via counter current exchange mechanism

PGF2a gets to ovarian artery without entering general circulation

luteolysis depends on

presence of uterus

if remove uterus the CL will remain in ovary indefinitely

ovarian branch of ovarian artery

drained by uterine vein

ovarian artery runs along the vein

prostaglandin to the ovary

estrous cycle

prostaglandin produced by the uterus on day 15-17 travels to the ovary and lyses the corpus luteum (if the cow is not pregnant)

recruitment selection dominance (3 waves)

E2 greater at day 21- heat and progesterone high prior to estrus

repro parameters of the cow

estrous cycle= non seasonal polyestrous (21 days, estrus lasts 8-12 hrs)
ovulation time from estrus onset= 24-30 hrs

1 ovulation /cycle 
CL life span=14-17 days 
ova to uterus~5 days 
gestation length= 9 months 
progesterone from CL until 150-250 days then is the placenta

type of placenta= epitheliochorial, cotyledonary

Fertilization

oviduct zygote- embryo remain ~4 days

pregnancy recognition

~15-17 days | luteolysis is stopped by bovine interferon tau

periods of pregnancy

zygote embryo (1st div) period of embryo organogenesis (6 wks)

duration of gestation

controlled by fetal pituitary- adrenal axis ~280 days

process of pregnancy

1. immediate transport of sperm 2. cervix- removal of non motile sperm, removal of some abnormalities 3. uterus- capacitation initiated 4. oviduct- capacitation completed, hyperactive motility 5. fertilization- acrosome rxn, spermatozoa penetrates oocyte (male and female pronuclei form)

Oocyte to hatched blastocyst

released and fertilized in the infundibulum- becomes zygote then morula then blastocyst in the oviduct

blastocyst

inner cell mass forms embryo proper placenta surrounds release interferon tau- which blocks prostaglandin F2a so CL not lysed and progesterone can act

Estrogen

acts on estrogen receptors (+ feedback)

estrogen receptors

+ feedback on progesterone receptors which have negative feedback on estrogen receptors + feedback on oxytocin receptors which influence PGF2a

conceptus hormones

IFNt from inner cell mass which acts through receptors and has a negative feedback on estrogen receptors blocking them IFNt prevent luteolysis by blocking estrogen and oxytocin receptors

progesterone hormone

negative feedback on progesterone receptors when levels too high without prostaglandin produced and CL lysed

IFNt and pregnancy recognition

ovary secretes estrogen but IFNt blocks estrogen receptors (silences receptors) in turn oxytocin receptor silenced to prevent development of luteolytic mechanism that requires oxytocin from the CL along with posterior pituitary to induce luteolytic pulses of PGF2a

Placentation

epitheliochorial- degree of invasion cotyledonary- shape villous- interdigitation nondeciduous- maternal loss of endometrium cows depend on passive transfer of immunity, 6 layers for transfer

epitheliochorial

endometrial capillary maternal through maternal basement membrane through endometrial epithelium to the fetal chorion through fetal basement membrane and into the chorionic capillary of the fetus

implantation in cows

28-33 days

placentomes

caruncles+cotyledons develop and get larger as pregnancy progresses ~40-45 days caruncle and fetal cotyledons connected by villi placenta regulates exchange of nutrients and waste products from fetus to dam concave shape

cortisol

necessary to initiate process of progesterone to estradiol

hormonal concentration at peripartum

at parturition progesterone decreases, fetal cortisol peaks until parturition and estrogen along with prostaglandin will decrease post parturition progesterone to estradiol increases oxytocin and pressure on the cervix, post delivery prostaglandin decreases

stage I

preparation uterus begins to make small contractions cervix dilates isolation, restless, tail raised, uncomfortable may see no signs, occurs 2-6 hours

uterine membranes appear

end of stage I, begin stage 2 1st allantoic fluid: watery brown or yellow fluid 2nd amniotic fluid: usually its what is seen; thick, clear which fluid (fluid= thick, lubrication and clear) average interval between rupture of 1st and 2nd is 15 min. amniotic sac begins expulsion

stage 2

active labor, delivery active abdominal contractions, calf enters the birth canal, cow continues to dilate (+ feedback loop), calf is born usually from last 15-90 minutes (avg. 45-60 min) but it may last for up to 6h

Stage 3

expulsion of the fetal membranes normal 2-12 hrs, retained 12-24 hrs