EQST405: Artificial Photoperiod & Hormone Therapy

melatonin

Artificial light interrupts the secretion of what hormone?

Jan. 1st

Age of horses used for racing & showing is based on what birthdate?

early December

When should the artificial photoperiod start

60-70 days

Hwo long does it take a mare to ovulate under an artificial photoperiod?

10 or more foot candles of light

What lighting level is appropiate for the artificial photoperiod?

newspaper test

What test can you do to see if lighting is adequate for the artificial photoperiod?

one 100-200 watt incandescent bulb

What wattage & how many bulbs is required in a 12×12 stall?

16L:8D

Traditional light vs dark hours for artificial photoperiod

constant regimen or stepwise regime

2 regimes for the traditional method of artificial photoperiod

3 hours of light first, add ½ hour each week until 16 hrs

stepwise regime

Pulse method/flash method

Method involves turning on light for 1 hour at select times

T/F: Artificial lighting eliminates the transition period

False

1) open mares

2) barren mares

3) maiden mares

4) early foaling mares

5) bred mares for 40 days after breeding or May 1st (whichever comes first)

What 5 horses would you use artificial light on?

3 consecutive days

How long does it take off lights for a mare’s ovulation time to regress?

1) Induction of estrus

2) Synchronization of estrus

3) Prevention of estrus

4) Embryo recipients

5) Lactation induction

5 reasons we use hormones in mares

mare must be in estrus

What is the requirement for induction of ovulation in mares?

1) endometrial (uterine) edema

2) relaxed cervix

3) pre-ovulatory follicle (>3.5cm)

3 features of estrus in a mare

deslorelin (GnRH analogue/Sucromate)

Human Chorionic Gonadotropin (hCG/Chorulon)

2 hormones used for induction of ovulation

42 hours

What is average ovulation time after giving deslorelin?

48 hours

ovulation happens within what time period after administrating deslorelin

Human Chorionic Gonadotropin (hCG/Chorulon)

hormone has an LH like effect

deslorelin (sucromate)

hormone is a GnRH analogue

24-48 hrs

hCG causes ovulation within what time period

36 hrs

hcG average ovulation time

2500 units

hCG dose

induce antibody formation

What hCG side effect causes reduced effectiveness?

1) Suppress estrus

2) Synchronize estrus

3) Hasten 1st ovulation of year

4) Pregnancy maintenance/support

5) Management of high risk pregnancies

5 uses of progestogens

Altrenogest (Regumate)

Used for estrus suppression

1ml/110lb orally for 10-15 days

dose for Altrenogest (Regumate)

Altrenogest (Regumate)

synthetic progestogen

late transition or cycling mares

Altrenogest (Regumate) is used in which mares?

estrus in 3-5 days
ovulation in 7-9 days

Altrenogest (Regumate) estrus & ovulation timelines

progesterone & estradiol

“gold standard” method of estrus synchronization

150 mg P4 & 10mg E2 for 10-14 days

progesterone & estradiol estrus synchronization doses

1) Luteolysis (CL destruction)

2) Prolonged & low amplitude uterine contractions up to 4 hours

What 2 things do prostaglandins do?

prostaglandins

Used to “short cycle” mares

luteal phase (when mature CL; >5 days post ovulation)

When are prostaglandins given?

2 doses 2 weeks apart

When should prostaglandins be given for synchronization of mares?

estrus in 3-5 days

ovulation in 7-10 days

prostaglandins estrus & ovulation timeline

post ovulation if breeding

When should prostaglandins never be used?

to evacuate uterine fluid

Why would you use prostaglandins to induce uterine contractions?

oxytocin

most commonly used to induce uterine contractions

1) inducing labor

2) retained placenta management

3) induce milk “let down”

3 uses of oxytocin

rapid onset (1 min) & short duration (45 min)

2 features of oxytocin uterine contractions

oxytocin

hormone has no effect on CL function

dopamine antagonist (antidopaminergic) → blocks production of dopamine

domperidone is what kind of hormone?

1) fescue toxicosis agalactia

2) unknown cause agalactia

3) induction of lactation in a nurse mare

4) induce follicle development in transition mares

4 uses of domperidone