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Flashcards in Reproduction Deck (38):
1

mare begin pubert at...
can become pregnant at...

18 months
2 years old

2

equine estrous cycle

-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

3

estrus

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

4

diestrus

-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

5

hormonal changes

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

6

hypothalamus

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

7

pituitary

transport LH, FSH, and GnRH down to ovary

8

ovary and follicles

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

9

endocrinology of estrous cycle

GnRH stims FSH and LH from anterior pituitary
-FSH stims follicle development
-dominant follicle produces estradiol and inhibin

10

estrous cycle and estradiol, inhibin, and prostaglandin

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

11

rule of thumb for estrogen/progesterone

high progesterone=suppresed LH
high estrogen=suppressed FSH

12

seasonality

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

13

seasonality influences

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

14

seasons for mares

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

15

photoperiod

controls ovarian activity through PINEAL gland and melatonin production

16

decreased daylight=...
increased=...

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

17

reproductive management

-artificial insemination, follicle stimulation, embryo transfer
-usually requires manipulation of estrus cycle

18

hormonal therapies

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

19

goals of manipulation

-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

getting mares ready for breeding

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

examine uterus by

rectal palpation or ultrasound

22

stallion puberty

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

23

stallion breeding soundness exam (BSE)

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

24

breeding basics

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

cooled semen for

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

26

frozen semen

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

27

teasing and estrus behaviour

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

28

lordosis

aka mating posture of female

29

conception

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

30

pregnancy

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

31

twins...

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

32

parturition

-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

stage 1 parturition

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

stage 2

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

emergency during stage 2

red bag: premature separation of placenta from uterus
-requires immediate attention because foal asphyxiates

36

stage 3

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

37

normal foal behaviour

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

weaning

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