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50 Cards in this Set

  • Front
  • Back
what is the function of dopamine released from the hypothalmus
inhibition of prolactin synthesis
oxytocin function
1.stimulation of uterine smooth muscle contractions
2.contraction of oviduct (gamete transport)
3.contraction of myoepithelial cells (milk let down)
ferguson reflex
stimulating release of oxytocin from the posterior pituitary upon stimulation of the cervix: not good in dystosia
is GnRH antigentic in other speices
no small protein hormone 10 amino acids
is FSH antigenic in other speices
yes
FSH functions
1.stimulation of follicular growth
2.stimulation of estradiol production by granulosa cells
3.induction of synthesis of LH receptors on granulosa cells
LH functions
1.stimulation of testosterone production (theca interna)
2.stimulation of estradiol production by granulosa cells
3.induction of ovulation of follicle
4.stimulation of progesterone secretion
5.maintenance of corpus luteum
gonadotropin pulses change in amplitude and frequency during luteal phase and follicular phase
luteal phase: amplitude increases and frequency decreases
follicular phase: amplitude decreases and frequency increases
how does fescue affect the mammary gland
mimmics dopamine: get no mammary gland developement, no milk production
does oxytocin cause milk production
no, just milk let down; prolactin causes prodcution
intermediate pituitary gland
not significant in most species
may become pathologically enlarged in the equine secondary to loss of dopamine regulation (equine cushings)
ovarian production of steriod hormones, function of theca and granulosa cells
theca cells: convert cholestrol to progestrone and then convert progesterone to androgens
granulosa cells: convert androgens to estrogens
inhibin
glycoprotein
comprised of alpha and beta subunits
produced by granulosa cells of the follicle
function:suppression of FSH secretion no effect on LH secretion
PGF2alpha functions
fatty acid hormone derived form arachidonic acid
functions: luteolysis
stimulation of uterine smooth muscle
involved locally in ovulation process
primordial follicle
oocyte
granulosa cells flat
basement membrane
primary follicle
larger than primordial
zona pellucida
cuboidal granulosa cells
secondary follicle
multiple layers of cuboidal granulosa cells surround primary oocyte
theca cells outside of basement membrane
tertiary follicle
FSH and LH receptors develop
FSH stimulates initial follicular development
fluid filled antrum forms within granulosa cell layer
preovulatory follicle
granulosa cells secrete estrogens
LH receptors form on granulosa cells
LH surge occurs in response to increased estradiol production and increased GnRH pulse frequency
In the dog,
_____________
levels rise prior
to ovulation
• In other species,
___________
levels begin to
increase 1 - 2
days after
ovulation
progesterone
The duration of luteal function in large
animals is ____ days, depending on
the species
14-18
PGF has no role in CL
regression in ______,
_____ or _______
PGF has no role in CL
regression in cats,
dogs or primates
Transfer of PGF from the uterus to the
ovary occurs by either:
Local counter-current system
(ruminants)
General systemic circulation
(horses and pigs)
COUNTER-CURRENT PGF TRANSFER
• PGF diffuses from the utero-ovarian
vein (high concentration) to the
ovarian artery (low concentration)
• With this mechanism, PGF can
regress the corpus luteum in the
ipsilateral ovary only
SYSTEMIC PGF TRANSFER
• PGF is secreted into the general
circulation
• Causes destruction of a CL on either
ovary
• PGF rapidly metabolized (lung)
• Produced in large quantities
INDUCTION OF PGF RELEASE
• Estradiol induces
formation of
oxytocin receptors
on endometrial cells
• Oxytocin secreted
from the corpus
luteum stimulates
uterine PGF release
CL life-span can be prolonged by:
• Pregnancy
• Pregnancy loss after maternal
recognition of pregnancy
• Chronic uterine infection
• Inadequate PGF release
CL life-span may be shortened by:
• PGF administration
• Endometritis (acute inflammation of the
uterus) causes premature PGF release
• Short estrous cycles (short luteal
phases) in a large animal suggests the
presence of a uterine infection
FOLLICLE SELECTION
• Dominant follicle produces estradiol and
inhibin which suppresses FSH
• Smaller follicles that still need FSH for
development begin to regress
• Dominant follicle continues to develop
under influence of LH
NUTRITION: EFFECTS ON REPRODUCTION
Nutrition effects many parameters:
• Attainment of puberty
• Duration of postpartum anestrus
• Gametogenesis
• Conception rates
• Embryonic mortality
• Sexual behavior
Lactation suppresses reproductive activity
in the following species:
• Pigs
• Cats
• Beef cattle
Lactation has little effect on reproductive
activity in the following species:
• Sheep
• Goats
• Horses
• Dairy cattle (milked not suckled)
AGE-RELATED CHANGES IN
REPRODUCTION
• Irregular cycles and prolonged
interovulatory intervals
• Decreased conception rate and decreased
litter size
• Anestrus (failure to cycle)
• Complete ovarian failure not commonly
recognized in domestic animals
CATTLE
• Puberty -
• Seasonality -
• Reproductive
lifespan -
CATTLE
• Puberty - 8 to 12
months of age
• Seasonality - not
seasonal breeders
• Reproductive
lifespan - 15 to 20
years
CATTLE
Proestrus:
• Period of rapid follicular growth
• Hormones - Progesterone low
Estrogens increasing
• Duration - 48 hrs
CATTLE
Estrus:
• Period of sexual receptivity
• Stands to be mounted by other cows
• Clear vaginal mucus
• Duration - 12 to 18 hrs
• Ovulation - 12 to 18 hrs after end of
estrus
CATTLE
Metestrus:
• Short period after estrus
• Bloody vaginal mucus - significance is
that it is too late to breed (source is
caruncular capillaries following rapid ↓ in E2
after ovulation)
• Duration - 2 days
• Progesterone - rising
CATTLE
Diestrus:
• Period of functional corpus luteum
• Not sexually receptive (no mounting)
• Duration - 16 days
• Progesterone - high
CATTLE
Optimal Breeding Time:
• From middle of estrus to 6 hours after
end of estrus (or 6 - 24 hrs after onset
of standing estrus)
• Ovum fertilizable for 8-10 hrs after
ovulation
CATTLE
Postpartum Period:
• Anestrus period
variable after calving
• Affected by season,
nutrition, suckling
• Dairy cows: 24 days
to ovulation
• Beef cows: 60 days
to ovulation
SHEEP
Seasonality:
• Short-day breeders
• Lamb in spring after
147 day pregnancy
• Some breeds cycle in
spring and fall
SHEEP
Estrus:
• Period ewe will stand for ram
• Mild mucus discharge, vulvar swelling
• Progesterone priming required for
expression of estrus
• Duration - 24-36 hrs
• Ovulation - near end of estrus
sheep • Ovulation rate:
1-2+
per cycle
• Increased plane of
nutrition increases
ovulation rate
(‘flushing’)
• Superovulation
possible with FSH or
eCG (PMSG)
GOATS
Estrus:
• Estradiol; No progesterone priming
• Vulva swollen, reddened, moist
• Rapid tail flagging
• Duration: 12- 24 (± up to 36) hrs
• Ovulation: near end of estrus
HORSES
Estrus:
• Period mare will stand for stallion
• Estrogen levels increasing
• Duration - 5 to 7 days
• Ovulation - 1-2 days prior to end of
estrus
HORSES
Breeding Options:
• Every other day beginning on the
second day of estrus until mare goes
out of heat
or
• Within 24 - 48 hrs prior to ovulation
LH prolonged surge occurs only in _____
horses
HORSES
Postpartum Period:
• No lactational anestrus
• Seasonal postpartum anestrus possible
(i.e. lack of follicular activity more dependent
on season than lactation)
• First ovulation (‘Foal Heat’ ovulation)
occurs 9-10 days after foaling
PIGS
Diestrus:
• Duration: 14 days
• CL not responsive to PGF until after
day 12 of cycle
horse COOLED-TRANSPORTED SEMEN
• Examine mares by palpation and
ultrasonography
• Begin on second day of heat
• Continue once daily until ovulation is
detected
• Order semen when a dominant follicle
reaches 35 to 40 mm in diameter
• Use hCG or GnRH to induce ovulation
at a predictable time