Reproduction Flashcards
When do mares begin puberty?
18 months ~ most can become pregnant as 2 year olds
What types of breeders are horses?
Seasonal polyestrus (long day breeders)
what does breeding occur? (usually)
- breeding season occurs when daylight increases (between April and July)
What is the estrus cycle and how long is it?
the time between ovulations
- 21 days (15-26 days)
What is the duration of the estrus cycle?
7 days (2-12 days)
When does ovulation occur?
near the end of estrus
What is estrus?
when the mare shows sexual receptivity to the stallion
What is estrus controlled by?
estrogen
What is the behavior of estrus?
- raising of tail
- urination
- posturing
- clitoral eversion (winking)
- moves in
- nickers
What is Diestrus?
the period of time when the mare rejects the stallion
How long is diestrus?
14-16 days
When does diestrus behavior start?
within 12 hours of ovulation
What is diestrus controlled by?
progesterone
What is the behavior of diestrus?
- pins ears
- clamps tail
- switches tail
- moves away
- kicks
- hollers
What hormone(s) peak right before ovulation?
LH, FSH, Estrogen
What is inhibin produced by?
the granulosa cells of the dominant follicle
What stimulates FSH?
GnRH stimulates FSH release from the anterior pituitary
What does FSH stimulate?
follicle development
What does the dominant follicle produce?
estradiol and inhibin
What does estradiol act on?
- LH secretion
- estradiol receptor sensitivity on dominant follicle
What does inhibin do?
decreases GnRH and FSH production and leads to LH surge and ovulation
What does prostaglandin cause?
lysis of corpus luteum and allows ovulation
What does high progesterone mean?
suppression of LH
What does high estrogen mean?
suppression of FSH
When are the transition periods?
spring )vernal) and fall (autumnal)
What happens reproductively during the transition periods?
time of low reproductive activity, no clear behavior patterns and delayed ovulation or anovulation
When do mares undergo regular cycles?
April/May –> Sept.Oct
What is reproduction in mares controlled by?
photoperiod through pineal gland and melatonin production
What influences ovulaition?
age, body condition, disease
How does decreased daylight effect ovulation? (process)
decreased daylight -> increased melatonin production -> decreased GnRH, FSH, and LH
What are some reproductive management strategies? (hormone therapy)
- manipulation of seasonality
- manipulation of normal cyclicity
- estrus synchronization
- modification of sexual behavior (eliminate estrus)
- Introduction of lactation
- management of high risk pregnancies
- Induction of abortion and parturition
What are the goals of reproductive management?
- induce and early start to the transitional period using imposed lighting regimes and GnRH administration
- Shorten the duration of the transitional period using administration and withdrawal of progesterone
- time estrus and ovulation with semen availability
- estrus synchronization between embryo donors and recipients
What is teasing?
exposure of mare to stallion
How do you get mares ready for breeding?
- teasing
- serial examinations to determine which mares are transitional or cycling early in season
- plan hormonal manipulation
- determine is a CL is present, uterine/cervical tone, monitor changes
- determine follicle size, monitor changes
- quantify uterine edema, monitor changes in patterns
When does puberty begin for stallions?
18 months (8-30 months)
How many spermatozoa are there per ejaculation (approx)?
100 million
What kind of sperm production do stallions have?
seasonal production - peak in july
What is sperm production controlled by?
GnRH
What is common for stallions in regard to reproduction?
low fertility (50%) and libido
What increases the chances of fertilization?
semen harvesting and artificial insemmination
What is the breeding soundness examination (BSE)?
an exam performed after 2 years on a stallion.
- physical exam
- semen collection and evaluation (morphology, concentration, motility)
What is the goal to reach in the Breeding Soundness Exam?
2 billion progressively motile, morphologically normal sperm in 2 collections 1 hours apart.
When are mares bred?
when in estrus so that ovulation occurs within 48 hours of breeding
What is fertility a function of?
- quality of the mare, timing of the insemination, and dose/quantity of the semen
What Happens during live cover?
mares are bred every other day with stallion
When do you use cooled semen?
plan to breed once, usually treat mare with hormones when mare has a follicle of 35mm. breed 24 hours later
When do you use frozen semen?
either fixed time insemination around 24-44 hours after ovulation induction
What is lordosis?
mating posture by the female horse
What are the conception rates per cycle and per season?
cycle = 60-70% season= 80-90%
In what breed is no reproductive technology used/allowed to be used?
thoroughbreds
How long does pregnancy last for?
320-365 days
perterm = 300-320 days
How do you detect pregnancy?
- ultrasound is best
How do you predict parturition?
- Electrolytes in milk change
- 72 hrs = incr. in Ca and Mg
- 24 hrs = decr. in Na and incr. in K - Colostrum in udder (waxing up)
What happens in stage 1 of parturition?
- coordinated forceful uterine contractions
- cervical dilation
- Visibly lasts about 4 hours
What behaviors are seen in the first stage of parturition?
Sweating, cramping, up and down behavior, dripping or streaming milk
What happens during stage 2 of pregnancy?
- rupture of the chorioallantois (water breaking)
- delivery of fetus
- lasts 5-30 mins
- once water breaks the amnion (bluish) should be visible at the vulva
How logn should delivery take?
30 mins or less
How does the foal usual leave the mother?
2 legs with hoves facing downwards followed by the muzzle
What is an example of an emergency during parturition?
- RED BAG: premature separation of placenta from uterus, requires imediate attention because foal asphyxiates
- Malpositioning requires attention also
What happens during phase 3 of parturition?
- passage of placenta
- normally takes up to 2 hours
- greater than 4 hours requires attention and treatment
What is normal foal behavior after parturition?
- sternal recumbency (1-2mins)
- suckle reflex (2-20mins)
- Stand (60mins)
- Nurse (2hrs up to 7 times per hour)
- Urination (within 8-12 hrs)
When does weaning take in feral horses?
8-9 months (until mother becomes pregnant/gives birth again
When does weaning take in domestic conditions?
4-6 months or earlier
What does weaning result in?
increased vocalizations, locomotion, and salivary cortisol
How do you reduce weaning stress?
introducing adults to foal
