Learning About Horses - Horse Life Cycle - Pregnancy & Birth

Fertility

1 foal (rarely twins) per year capable of producing foal at 18 months  healthier for mare and foal by at least 4 years can continue until late twenties

twins  thoroughbreds (25-35% conception) quarter horses (5-10%) all horses should be examined for twins with transrectal ultrasound

Breeding

Gestation

mate in summer, spring birth 320-380 days average 340 330 is most commonly cited gestation length NEVER recommend inducing labor fescue toxicity  most common cause of prolonged gestation reduced milk production but by due date it is too late to restrict the fescue grazing of the mare since it usually requires 60-90 days of restricted grazing

Confirming Pregnancy

ultrasound after 2 weeks by blood or urine test after 2-3 months

Care of the Mare

athletic horses have best reproductive organ conformation without sacrificing calories to stay alive avoid transporting mare quarantine from new arrivals no need to supplement diet until lactation obese mares have difficult times trying to expel a fetus deworming should continue pasture turn out provides all necessary exercise regular diet should be maintained water supply is CRITICAL fetal fluids and milk production

vaccinations Herpesvirus (EHV-1) can cause late term abortions and mares vaccinated for this disease 5, 7, and 9 months gestation ALL vaccinations should be administered to the mare protecting against diseases for which you want the foal vaccinated vaccinations given to mare at foaling DO NOT PROTECT foal since colostrum does not have adequate time to manufacture the correct antibodies

Caslick's procedures (vulva is sewn partially closed) should be opened 30 days before foaling

Ascarid larvae can be passed in milk mare should be dewormed with product with ivermectin ascarid impaction was a common cause of colic and death in foals before ivermectin  neonatal isoerythrolysis (NI) screens are done within two weeks of foaling these blood test determine if the mare has hypersensitized herself to the blood-type of the foal older mares are more prone to being hypersensitized to a foal's blood-type if a mare is NI (+), the foal must be muzzled for the first 24-36 hours of life and colostrums donor must be sought

Pregnancy

ov = optic vesicle with the retinal pigment epithelium ea = ear nr = neck region sr = scapular region ar = abdominal region fr = femoral region mtr = metacarpal region na = nail apparatus  metr = metatarsaus region tl = tail

Day 6 fertilized egg enters uterus Day 9  can be seen with naked eye "embryonic vesicle" houses embryo vesicle looks like a shimmering, firm, translucent bubble less than 1/4 inch in diameter on ultra sound see black circle in sea of gray (mare's uterus) no bigger than a pinpoint
Day 10 3.8mm in diameter tiny bright fleck in middle is the inner cell mass which will eventually form the fetus remaining cells will form placental membranes
Day 14-16 confirms initial pregnancy and looks for twins if twins seen "crushing" reducing twins protects other twin and mare mare examined 48-72 hours after procedure almost all >90% of twins are aborted almost all twins die limited room in uterus if twins survive they are usually weak or non-viable  Day 16 if embryo does not touch all portions of the uterus the mare will reject the embryo and go into another heat cycle Day 17 embryo attaches on uterus wall
Day 20
Day 24 vesicle grown to 1 inch shimmering, flabby, translucent bubble with dark red dot (embryo) a network of threadlike blood vessels emanates from the 1/4 inch dot make out the beginnings of head, tail, four buds on ultrasound you will see a vesicle as an irregular guitar shaped black blob in sea of grainy grey  embryonic heart is large enough to be seen to find focus on "floor" of blob white smudge about 1/2 inch in diameter resting there is embryo within the smudge a tiny black dot about the size of a pinpoint it will be flashing off and on it is the embryo's beating heart Day 26 Vet can perform transrectal ultrasound to visualize heartbeat and confirm fetal viability

sm = somites lm = limbs ht = heart h = hindbrain m = midbrain f = forebrain 4th = Brain 4th ventricle cc = cervical curvature ov = optic vesicle ba = branchial arches thl = thoracic limbs li = liver pel = pelvic

Day 26-30 confirms heartbeat and fact that fetus  is alive Day 30 - 1 Month embryo will not attach itself to side of womb it will move up and down in the uterus sending hormonal signals that cause tiny contractions and stops the mare from coming back into season slight increase in blood flow to uterus mare will not have any physical changes basic body plan with limb buds and beginnings of a tail 12mm from crown to rump tiny hear already pumping blood, can be seen on scans rudimentary beginnings of other essential organs stomach, liver, pancreas, lungs fuzzy-looking outer sac placental membrane - amnion foal encased in this slippery, translucent-white membrane when born mare still shows no sign of pregnancy mares do not have morning sickness Day 30-35  Experienced equine veterinarians can feel a mechanical bulge in uterus

Day 35

36 days - 1.2 months

ov = optic vesicle with the retinal pigment epithelium cc = cervical curvature ea = ear thl = thoracic limbs ht = heart uc = umbilical cord li = liver rb = ribs pel = pelvic ribs fr = femoral region tl = tail na = nail apparatus

Day 40 1.3 months vesicle is not 2 1/2 inches roughly spherical in shape - somewhat collapsed 3/4 inch embryo recognizable as four legged critter blobby dome head eyelids rudimentary ears ridges where nostrils will be functional elbows on stifle joints ultrasound roundish black blob  white smudge embryo suspended from blob's ceiling "rise and fall of the embryo"  filmy membranes at top of vesicle coming together to form the umbilical cord as they do they shorten, pulling the olive-sized embryo up to the ceiling like a chandelier

Day 45 elective exam no specific reason since endometrial cups should already be formed by this time if mare aborts 40-45 days or after it is unlikely she can get pregnant again the same breeding season   Day 50 - 55 Pregnancy slightly over an inch long nesting withing the confines of the 3-inch vesicle can see tiny ribs under its skin its domed head looks like that of a Chihuahua  distinct skull little triangle ears hock and fetlock joints have developed it is now a fetus on ultrasound see fetus on its back on the vesicle's floor due to lengthening of umbilical cord about the size of a pecan last opportunity to see fetus on ultrasound will be too big for the screen

ea = ear ov = optic vesicle with the retinal pigment epithelium oc = oral cavity nr = neck region sr = scapular region rb = ribs fr = femoral region tl = tail na = nail apparatus

Day 60 - 2 Months 2.5 inches long; 1 ounce (64.5mm) vesicle is now flabby and shapeless conforming to the uterine walls fetus is about 2 1/2 inches long clearly resembles a horse tiny hooves, complete with soles and frogs head is still tucked but less so fetus is hairless  skin is thicker starts loosing transparency formation of brainstem, encephalic fourth ventricle, spinal cord and transition from brain vesicles to brain are beginning orbital vesicle is present gums are forming about size of hamster cartilage is light blue, bone is purple
Day 65 - 2.1 months 69mm crown to rump skin remains pale and hairless eyes sealed shut internal organs are developing muscles are growing hoof-shaped feet are forming and the frog rubbery pad on the bottom of the foot  acts as pump to move blood up the thin length of the horse's leg back to heart sex of fetus can be determined twins are unusual and unwelcome mares are not designed to carry two foals to term vets will usually preform a "twin reduction" to avoid losing both  Day 60-70 or 110-140 elective exam no specific reason, but has become more important since the advent of fetal sexing became available @10 years ago starting day 58 genital tubercle will migrate towards tail to become the clitoris OR migrate towards prepuce to become the penis it is virtually impossible between days 80-90 and after day 140
Day 75 2.5 months red stain has been used to highlight the developing skeleton now almost 75mm long darker areas show calcium deposits where bones are starting to ossify hardening skeleton system provides a framework for other body structures and protects the internal organs as they develop miscarriage is very unlikely now
Day 80 4 inches long; 2 ounces fetal head and neck will be untucked being held level with the spine in "normal" horse position its sex is now viable little lumps for the scrotum/udder fetus is size of chipmunk
Day 85 - 2.8 months fetus now measures about 100mm features are quite distinct remains hairless and pale in absence of pigment mare will be experiencing hormonal changes and increased blood flow to the uterus now size of melon but will not yet look pregnant

Day 90 (3 months) starts to look like a small horse
Day 95 - 3 months
Day 100 7 inches long; 1 pound size of 6 week old kitten starting to get hair on its lips ears are unfurling (1/2 inch long) the coronary bands look like raised lines encircling the tops of its tiny 1/4-inch hooves

Day 107 - 3.5 months  ov = optic vesicle with the retinal pigment epithelium ea = ear nr = neck region sr = scapular region ar = abdominal region fr = femoral region mtr = metacarpal region na = nail apparatus  metr = metatarsaus region tl = tail

Day 150  12 inches; 6 pounds gaining more than a pound every 10 days size of a rabbit hair on chin, muzzle, eyelids eyelashes have emerged

Day 165 5.5 months

Day 180 (6 months) 19 inches long; 25 pounds main and tail hairs appear size of a beagle       mare starts to look pregnant

Day 183 - 6 months

Day  245 - 8 months

Day 250 (8 months) mare looks pregnant Day 270  27 inches long; 70-80 pounds looks like foal fine hair covers body now has a swatch of hair on its tail size of German Shepherd

Day 300 - 10 months

Day 315  Signs of foaling begin

Day 320 Last week or so fetus's lungs have developed to the point that they can function in the "real world" its legs have strengthened to the point that they can support its weight hair has coarsened from fine silky texture of fetus to bonafide foal fetus is "done" foal will be born in a matter of days or weeks

Day 340 Birth - 11 months  mares need minimal assistance and give birth quickly usually within 20 min  lying down foal delivered in amnion  white shiny membrane interlaced with a network of blood vessels  which it breaks as it is born mare will often stay lying down with foal's feet still inside her umbilical attached and passing blood to the foal within hour foal will be up and being licked and nuzzled by its mother

Impending foaling/abortion vaginal discharge dripping milk mares can abort without any clinical signs of being sick herself udder will usually fill 2-4 weeks before foaling teats will distend 4-6 days before foaling "wax" will appear on teats 1-4 days before foaling calcium increases 24048 hours before foaling commercial kits can check for increase in calcium water hardness tests can also be used NOT RELIABLE  relaxed appearance of vulva movements in the flank "of the foal kicking"  preparing for foaling minimize stress and observation mare's usually do very well without help "fetus determines the say of delivery mare determines the hour" outdoor foaling used for centuries foaling stalls MUST be at least 14 X 14 disinfect floor between deliveries straw best surface shavings stick to eye may cause corneal ulceration in the neonate

Foaling (Labor & Delivery) 

 

First Stage of Labor

• >85% of mares foal at night
• survival adaptation
• foal should be ready to run with mare by daylight
• mare is anxious
• kicks at belly
• may "nest"
• may be mistaken for colic 
• continuous up and down
• excessive urination
• many will sweat within hour of giving birth
• mare is "heating up"
• wrap tail & clean perineal area
• last about an hour
• Stage 1 over
• when chorioallantois breaks "rush of fluid"

Second Stage of Labor

• usually 15-25 min
• maybe wise to start a stopwatch
• expect to see continuous progress
• front hooves, nose, ears, etc
• RED BAG
• EMERGENCY
• NO TIME TO CALL VET 
• MUST BE CUT
• FOAL DELIVERED IMMEDIATELY
• caudal presentation 
• make sure foal is breathing
• stimulate nostrils with blunt object
• rub vigorously with towel
• when foal is born 
• DO NOT CUT CORD
• "breech delivery"
• disinfection should be preformed
• CHLORHEXADINE > IODINE

Third Stage of Labor

• If placenta is NOT passed withing 3 hours = EMERGENCY

ONE, TWO, THREE RULE

• ONE - foal should stand in ONE hour
• TWO - foal should be able to nurse by TWO hours
• THREE - foal should be ACTIVELY consuming colostrums by THREE hours

Meconium Impaction

• most common form of colic in newborn foal
• foals should be administered enema (or two) to aid in passage of meconium

Colostrum

• harvest if foal does not aggressively consume it
• vet can administer colostrum via a nasogastric tube

Milking a mare

• 16-36 ounces of colostrum from udder
• 80-85% of colostrum absorption is in the first 8-12 hours of life
• get in practice of pulling blood for an IgG 6-8 hours after foaling 
• you should have adequate IgG to test
• you also have 3-4 hours remaining to administer colostrum via nasogastric tube is required

Postpartum Mare Care

• Usually none is needed
• Phenylbutazone (Bute) or Flunixin Meglamine (Banamine)
• MAY be required to reduce swelling of vulva or rectum
• CALL VET
• take temp BEFORE administering ANY DRUGS
• should be under 101.5 degrees F
• rectally
• Bute and Banamine can reduce fevers
• retained placenta or endometritis is common in febrile mares immediately after foaling
• mare are prone to colonic displacement after foaling
• rupture cecum or bladder DURING foaling

Foals

• normal for fetlocks to be so weak they are touching the ground
• usually rectify themselves with age and exercise
• do not require bandages or splints
• fractured ribs are common in Thoroughbreds (not in others)
• contracted legs of deviations in legs that prohibit nursing should be dealt with immediately by vet
• most foals designed to be turned out with mare in the morning after foaling
• stall restriction is NOT necessary
• unless foal has orthopedic concerns where movement and exercise MUST be limited 

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