ANS 110: Reproduction

What are the mare reproductive organs?

Vulva, Vagina, Cervix, Uterus, Ovaries, Fallopian Tubes

What is special about the ovary of the mare?

They have ovulation fossa

What are ovulation fossa?

An indent on the ovary where the egg goes through to be expelled

What cycle accounts for changes within the ovary?

Ovarian cycle

What is the other name for the fallopian tubes?

Oviducts

When do follicles develop?

Throughout the ovarian cycle/follicular phase

What stimulates follicle development?

FSH

What produces FSH?

Pituitary gland

What is a graafian follicle?

Large follicle right before it released the egg

What is ovulation?

When the egg is released from the follicle

What stimulates ovulation?

LH and estrogen

Where is LH produced?

Pituitary gland

What happens to the follicle after ovulation?

Becomes a CL

What does the CL produce?

Progestrerone

What is the estrous cycle?

Recurring changes of the ovaries in response to reproductive hormones

What are the key hormones of the estrous cycle?

LH, FSH, Estrogen, Progesterone

What are the ovarian changes during estrous?

follicular development, ovulation, CL formation, regression

What is estrus?

When an animal/mare is sexually receptive (in heat)

What are signs of estrus due to?

estrogen

How long is estrus in horses?

5-7 days

When does ovulation occur for a mare?

1-2 days before the end of estrus

What are the signs of estrus?

Show interest in stallion, elevate tail, “break down”, wink

What is breaking down?

Assuming the breeding posture and urinating

What is winking?

Evert the clitoris

What is it called when a mare does not show signs of estrus?

Silent heat

What happens if egg meets sperm?

Fertilization

What happens if conception does not occur after ovulation?

The CL regressed, the egg is reabsorbed, and a new cycle as another follicle matures

What is the luteal phase called?

Diestrus

What is anestrus ?

A sexual cycle rest

What type of breeders are horses?

Seasonal, long day breeders

What are horses estrous cycles controlled by?

Melatonin

When do horses go into anestrus?

When the days are shorter and nights longer, so winter

What are the challenges to breeding a mare?

Season, heat detection, egg survival, and sperm survival

What are the seasonal challenges with breeding mares?

They are seasonal breeders so you need to keep them under lights in order to prolong cycling, so keeping lights on or blue light masks

What are the heat detection challenges with breeding a mare?

Silent heat

How long do eggs survive?

24hrs

How long does sperm survive?

48hrs

Why do we want to be careful about our timing for breeding?

There is a small window of time for eggs and sperm, if we miss the mare we have to wait 22 more days, and it may save money from shipping to stallion

How can we determine if a mare is ovulating?

Teasing the mare or using an ultrasound to determine follicle status

How do we tease a mare?

Use a teaser stallion that teases mare to see if she is receptive, and use a teasing chart to keep track

What do the testes produce?

Testosterone and sperm

Describe how the testes move with birth

Inside body until just before birth, then descend into the scrotum

What is a ridgling/cryptochid?

A horse where only one testes descends into the scrotum and the other remains in the body (sometimes two) and they are often surgically removed

What happens during mating with a stallion?

The stallion gets an erection, then ejaculates

What is semen?

Sperm plus seminal fluid from glands

When is sperm production highest in a stallion?

Around 4 years of age, bit they can remain fertile into their 20s

What is sperm production affected by?

Frequency of ejaculation

What are the methods of breeding? 

Live cover and AI

What are the two types of Live Cover?

Pasture mating and hand mating

What is pasture mating?

A stallion has free access to a mare in a pasture

What are the advantages of pasture mating? Disadvantages?

Advantages: Easy to get pregnant, stallion handles reception, Disadvantages: Don’t know conception date, could cause injuries to horses

What is hand mating?

Stallion is led directly to mare

What are the advantages of hand mating? Disadvantages?

Advantages: Know exact conception date, Disadvantages: Safety of people and horses

What is AI?

Semen is collected from the stallion into an artificial vagina, semen quality is inspected and then shipped to the mare, where it is then inseminated into the mare

Why is it important to inspect the quality of semen?

It must be kept at body temperature or frozen with semen extenders

What does it mean for a mare to be inseminated?

The straw is placed past the cervix, and the sample goes directly into the body of the uterus

What is embryo transfer?

A donor mare is bred, and after pregnant the embryo is flushed out and placed in a recipient mare, who has the foal so the mare can continue a career and keep cycling

What does the embryo do after fertilization?

Migrates for 2 weeks until it stays in one spot and implants in an area with the highest blood flow

How long does it take for the embryo to implant?

40 days

What does the fetus develop with the placenta for?

To supply it with nutrients, oxygen, and remove wastes

What type of placenta do horses have?

A diffuse placenta where it wraps all the way around the embryo

How can we detect pregnancy?

Ultrasounds, palpation, and eCG hormones

Why is important to use ultrasound for detecting pregnancy?

to ensure only one embryo is present and it is the quickest method

Why do we not want to have twins?

There’s not enough space and the foal can develop wrong, both are weaker and have lower birth weights, and some breed registries only allow 1 foal to be registered, dangerous for mare and foal

What does palpation do?

Detects the developing uterus

When is the eCG hormone detectable? How do we detect it?

Within 35 days of pregnancy, and with a urine test

How do we get rid of the extra twin?

Pinch other embryo

What are twins caused by? What breed is it common in?

Caused by double ovulations, can occur up to 25% in TBs

How long is a horses gestation?

333-340 days

What happens during the first trimester of pregnancy?

Slow growth of fetus

What happens during the second trimester of pregnancy?

More rapid growth of fetus, mare gains most weight as she cannot eat much during third trimester

What happens during the third trimester of pregnancy?

Most rapid growth of fetus

How much does the foal weigh at birth?

10% of mares weight

What are signs that foaling is close?

Waxing, milk test kits, milk veins enlarge, tailhead relaxes, colicky behavior

What do milk test kits look for?

More basic and more calcium milk

What happens during the 1st stage of foaling?

Foal moves into position until water breaks, and it may last several hours

What happens during the 2nd stage of foaling?

The fetus moves through the birth canal and is born, there are intense uterine contractions and it happens very quickly

What happens during the 3rd stage of foaling?

Expulsion of the placenta, typically after about 30 min, and we need to inspect the placenta for tears, damage, if retained or not

How many mares have dystocia?

Less than 5-10%

What is dystocia usually?

Usually malposition of foal, and we just push foal back in so it can reposition

What do we do if a foal is breached?

May need C section, but mares may not be able to bring future foals to term and will need C sections in future

What should a foal do after birth?

Stand and nurse within 60 mins, umbilical cord should break and then be treated with iodine, ensure foal gets colostrum for immunity, should pass meconium within first 3 hours

What do we need to assess for a foal after birth?

Passive transfer through a blood sample

What is a caslicks procedure?

Where we temporarily tie up the top portion of the vagina so feces does not get into it while pregnant