horse production quiz 2

Sire → stallion (top side)

by

Mare (bottom side)

out of

causes of early pregnancy loss

hormonal imbalance, age, twin pregnancy, reproductive health, time between ov and fertilization

estrous (entire cycle)

21-22 days

estrus (follicular phase)

heat stage 3-7 days

mare ovulates

24-48 hrs prior to end of estrus

diestrus (luteal phase) between estrus phase

15-19 days (*14 Days)

anestrus

not cycling

day 1-14

diestrus

day 15-20

estrus (day 20 ovulation)

seasonal polyestrous

start to cycle as daylight gets longer until fall when days shorten

cycle march/april through september

winter anestrus

take a break during winter and early spring

hypothalamus produces GnRH

stimulates release of gonadotropins from pituitary

two gonadotropins

FSH and LH responsible for follicular growth and OV

dominant follicle

usually OV on 35-45mm follicle

surge of LH causes follicle to rupture → OV

true

CL forms → secretes progesterone

maintains pregnancy

empty follcile → CL

CL = temporary structure

luteolysis

CL destroyed and cycle begins again 14-16 days after OV

Sperm can live for how many hours outside of the body

48 hrs

Uterine endopetrium (uterine lining) secrets prostaglandin

which destroys CL

Jan 1 is official birthdate for many breed associations

breeding season/sheds open feb 15th (or 14th) some as early as feb 10th

optimal age for breeding

4-15 yo

fertility decreases

15-20 yo

dramatic decrease in fertility

by 20 yo

lighting and hormones used to control cycle

breed sooner

induce OV

sync estrus and OV

increase conception during foal heat

Lighting

need 16 hours of light to start cycling earlier

suppresses melatonin affects gonadatropin

Lighting must be bright enough to

read newspaper from 7am-11pm

Begin lighting

DECEMBER 1 to be cycling by feb 15

regumate

progesterone

control cycle (behavior)

maintain pregnancy

PGF2a - prostaglandin

need follicle to OV in 8-9 days

hGC

give > 35mm follicle to OV in 24-48 hrs

GnRH

give > 30 mm follicle to OV 48hrs

uterine culture/biopsy

swab uterine lining to check for bacteria or inflamation

culture 1 month prior to breeding

gives time to treat or cycle again

uterine biopsy

scale 1-4

1-good 80% conception rate

2- ok 50-80%

3- questionable 10-50%

4 bad <10%

why higher ratio of fillies in maden and ages mares?

female embryos adapt better to suboptimal uterine conditions (smaller uterus)

maden mares

tend to produce small fillies

NSAIDS (bute, banamine)

can interfere with OV

Breeding roll

used in live cover to protect mare and prevent vaginal tear