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Equine biology > Reproduction > Flashcards

Reproduction Flashcards

1
Q

mare begin pubert at…

can become pregnant at…

A

18 months

2 years old

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2
Q

equine estrous cycle

A
  • seasonal polyestrus (long day breeders) between april and july
  • estrous cycle is 21 days
  • duration of estrus is 7 days
  • ovulation occurs near end of estrus
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3
Q

estrus

A
  • when mare shows sexual receptivity to stallions
  • stronger signs as ovulation nears
  • controlled by estrogen
  • behaviour=raising tail, urination, posturing, winking
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4
Q

diestrus

A
  • when mare rejects stallions
  • 14-16 days, behaviour starts within 12 hours of ovulation
  • controlled by progesterone
  • behaviour=pins ears, clamps tail, switches tail, moves away, kicks
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5
Q

hormonal changes

A

estrogen, LH, and FSH high during estrus, with progesterone low; progesterone high and fsh, lh and estrogen low; FSH peaks twice at beginning and end of diestrus, and PGF2 spikes at end of estrus

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6
Q

hypothalamus

A

‘surge center’ where GnRh is released into pituitary gland and receives signals from ovary
-also commands release of LH and FSH from pituitary

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7
Q

pituitary

A

transport LH, FSH, and GnRH down to ovary

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8
Q

ovary and follicles

A

cause +ve feedback with hypothalamus or -ve with pituitary gland’s secretion of GnRH and FSH via inhibin

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9
Q

endocrinology of estrous cycle

A

GnRH stims FSH and LH from anterior pituitary

  • FSH stims follicle development
  • dominant follicle produces estradiol and inhibin
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10
Q

estrous cycle and estradiol, inhibin, and prostaglandin

A

estradiol=LH secretio, estradiol-receptor sensitivity on dominant follicle

  • inhibin=decreased GnRH and FSH; leads to LH surge and ovulation
  • prostaglandin (PGF2) causes lysis of CL and allows for ovulation
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11
Q

rule of thumb for estrogen/progesterone

A

high progesterone=suppresed LH

high estrogen=suppressed FSH

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12
Q

seasonality

A

transition periods in spring=vernal and fall=autumnal

  • time of LOW reproductive activity, no clear patterns, and delayed ovulation
  • normal cycles in april/may, september/october
  • controlled by photoperiod
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13
Q

seasonality influences

A

age, body condition, disease
-2 years old cycle in june-august
-mares over 20 have few cycles in june or july or no ovary activity
over 25 seldom cycle

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14
Q

seasons for mares

A

summer=natural breeding season, fall transition, winter=anovulatory season, spring transition

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15
Q

photoperiod

A

controls ovarian activity through PINEAL gland and melatonin production

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16
Q

decreased daylight=…

increased=…

A

=increased melatonin production=decreased GnRH, FSH, and LH

=decreased melatonin production=incrased GnRH, FSH, estrogen, and LH

17
Q

reproductive management

A
  • artificial insemination, follicle stimulation, embryo transfer
  • usually requires manipulation of estrus cycle
18
Q

hormonal therapies

A

-manipulation of seasonality, normal cyclicity, estrus synchro, modify sexual behaviour through elimination of estrus, induction of lactation, manage high risk pregnancy, abortion

19
Q

goals of manipulation

A
  • induce early start of transitional period using lighting regimes and GnRH administration
  • shorten duration of transitional period using and withdrawal of progesterone
  • time estrus and ovulation with semen availability
  • estrus synchro btw embryo donors and recipients
20
Q

getting mares ready for breeding

A

teasing through exposure to males

  • in early season examine to determine which mares are transitional and which cycling
  • plan hormonal manipulation
  • determine if CL present, follicle size, quantify uterine edema
21
Q

examine uterus by

A

rectal palpation or ultrasound

22
Q

stallion puberty

A

begins at 18 months, seasonal sperm production controlled by GnRH, peak sperm in july

23
Q

stallion breeding soundness exam (BSE)

A

performed after 2 years: physical exam and semen collection and evaluation (morphology, concentration, motility)

24
Q

breeding basics

A

breed mare when in estrus, so ovulation occurs within 48 hours of breeding

  • fertility is function of quality of mare, timing of insemination, and dose/quality of semen
  • liver cover=breed mares every other day
25
Q

cooled semen for

A

=breed once, when mare has 35 mm follicle, breed 24 hours later

26
Q

frozen semen

A

either fixed time insemination around 28-44 hours after ovulation induction

27
Q

teasing and estrus behaviour

A

-leaning or moving in, raising tail, winking, urination, posturing

28
Q

lordosis

A

aka mating posture of female

29
Q

conception

A

per cycle rates 60-70%
per season pregnancy rates 80-90%
-no artificial reproductive tech allowed in Thoroughbreds, varied for other breeds

30
Q

pregnancy

A

normal range of 320-365 days
preterm=300-320 days
-progesteron maintains pregnancy detection
-ultrasound best

31
Q

twins…

A

must be reduced before day 35, danger to mother and foals

32
Q

parturition

A

-predicted by electrolytes in milk change
-72 hours=increase in calcium and magnesium
-24 hours=decrease in Na and increase in K
colostrum in udder (waxing up)
-occurs in 3 stages
-90% foalings proceed without intervention of birth
-only intervene when foal or mare are in great danger

33
Q

stage 1 parturition

A

coordinated forceful uterine contractions

  • cervical dilation
  • visibly lasts about 4 hours
  • behaviour is typical of colic: sweating, cramping, up down behaviour, drippin or streaming milk
34
Q

stage 2

A

rupture of chorioallantois, aka water breaks

  • delivery of fetus
  • lasts 5-30 minutes
  • once water breaks amnion (bluish) should be visible at vulva
  • delivery occurs in 30 minutes or less
  • normally see 2 legs facing down followed by muzzel
35
Q

emergency during stage 2

A

red bag: premature separation of placenta from uterus

-requires immediate attention because foal asphyxiates

36
Q

stage 3

A

passage of placenta, takes up to 2 hours, greater than 4 requires treatment

37
Q

normal foal behaviour

A 
sternal recumbency: 1-2 minutes
suckle reflex: 2-20 minutes
stand in 60 minutes
nurse in 2 hours, for up to 7 times per hour
urination within 8-12 hours
38
Q

weaning

A

free-living weaning occurs at 8-9 months

  • in domestic occurs at 4-6 months
  • results in increased vocalization, locomotion, and salivary cortisol
  • weaning stress can be reduced by introducing adults
  • post-weaning handling can improve handling up to 18 months later

Equine biology (16 decks)

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