Reproduction

Question 1

mare begin pubert at…

can become pregnant at…

Answer 1

18 months

2 years old

Question 2

equine estrous cycle

Answer 2

• 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

Question 3

estrus

Answer 3

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

Question 4

diestrus

Answer 4

• 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

Question 5

hormonal changes

Answer 5

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

Question 6

hypothalamus

Answer 6

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

Question 7

pituitary

Answer 7

transport LH, FSH, and GnRH down to ovary

Question 8

ovary and follicles

Answer 8

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

Question 9

endocrinology of estrous cycle

Answer 9

GnRH stims FSH and LH from anterior pituitary

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

Question 10

estrous cycle and estradiol, inhibin, and prostaglandin

Answer 10

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

Question 11

rule of thumb for estrogen/progesterone

Answer 11

high progesterone=suppresed LH

high estrogen=suppressed FSH

Question 12

seasonality

Answer 12

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

Question 13

seasonality influences

Answer 13

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

Question 14

seasons for mares

Answer 14

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

Question 15

photoperiod

Answer 15

controls ovarian activity through PINEAL gland and melatonin production

Question 16

decreased daylight=…

increased=…

Answer 16

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

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

Question 17

reproductive management

Answer 17

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

Question 18

hormonal therapies

Answer 18

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

Question 19

goals of manipulation

Answer 19

• 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

Question 20

getting mares ready for breeding

Answer 20

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

Question 21

examine uterus by

Answer 21

rectal palpation or ultrasound

Question 22

stallion puberty

Answer 22

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

Question 23

stallion breeding soundness exam (BSE)

Answer 23

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

Question 24

breeding basics

Answer 24

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

Question 25

cooled semen for

Answer 25

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

Question 26

frozen semen

Answer 26

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

Question 27

teasing and estrus behaviour

Answer 27

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

Question 28

lordosis

Answer 28

aka mating posture of female

Question 29

conception

Answer 29

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

Question 30

pregnancy

Answer 30

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

Question 31

twins...

Answer 31

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

Question 32

parturition

Answer 32

-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

Question 33

stage 1 parturition

Answer 33

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

Question 34

stage 2

Answer 34

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

Question 35

emergency during stage 2

Answer 35

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

Question 36

stage 3

Answer 36

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

Question 37

normal foal behaviour

Answer 37

``` 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 ```

Question 38

weaning

Answer 38

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