Exam 1 Flashcards
What is the embryonic phase around days 4-5 of gestation
Morula
What is the embryonic phase around days 5-6 of gestation
Blastocyst
What forms on an equine embryo at day 6 of gestation
The glycoprotein capsule
What is the function of the glycoprotein capsule
Makes the embryo strong, resilient, and spherical so it will survive the maternal recognition
What is the maternal recognition process in mares
The emrbyo bounces around the entire uterus including both uterine horns connecting to as much of the uterus as possible and preventing both overies from producing PGF2alpha
What begins developing at day 10
The embryonic disc
What begins developing on day 14
The yolk sac
What occurs on days 16-17
Fixation and amnion starts to develop
What is fixation
When the embryo stops moving around the uterus due to the uterus getting firmer and the size of the embryo
What happens between days 8-16 of gestation
The trans-uterine movement occurs due to PGE and PGF produced by the embryo
What does PGE do during the trans-uterine movement
It relaxes the isthmus-ampulla junction in the oviduct allowing the embryo into the uterus
What does PGF do during the trans-uterine movement
Causes the embryo to be able to move around the uterus for maternal recongition
When is the amnio completely developed
Day 18
What occurs on day 21 of gestation
The allantois emerges and the capsule that keeps everythings spherical falls off
What occurs on day 25 of gestation
The chorionic girdle starts to develop allowing us to visualize a heart beat via ultrasound
Wha occurs on day 30 of gestation
The yold sac gets smaller and the other membranes get larger
What occurs on day 35 of gestation
The endometrial cups form from the girdle
What is the function of the endometrial cups
The secrete equine chorionic gondaotropin (eCG) from the placenta which invades the endometrium of the uterus working alongside progesterone secretion
What occurs on day 40 of gestation
The placentation begins forming
What can be done starting day 60 of gestation
Fetal sexing can be done transrectally
What happens around day 80 of gestation
The fetus fills both horns
What happens around day 95 of gestation
Placentation is complete and the mare starts providing the fetus w/ oxygen and nutrients
What is the importance of embryonic movement
It signals the maintenance of the first CL around day 14 of gestation
What is the importance of endometrial cups
It produces equine chorionic gonadotropin (eCG)
Why is fixation important
Signals that the uterus has gotten firm enough and the embryo has gotten large enough that it is not able to move around in the uterus anymore
What is the function of eCG
It acts on the receoptor for LH supporting the present CL and causes secondary CL formation
What is the time like of production for eCG
Starts being produced around day 35-40 and stops being produced around day 90
What takes over in supporting the CL after eCG is no longer produce
5 alpha pregnances
What type of half life does eCG have
It has a long half life meaning that it will stay in the body for days
What can eCG cause in other species
Super ovulation
What is the first luteal response
This is the luteal response that occurs w/ normal ovulation
What is the second luteal response
When eCG begins to produce and stimulates the first CL to keep producing progesterone
Do horses ovulate during pregnancy
Yes, produces secondary CL’s
When do progestersone levels produced by the CL drop
Day 120
What takes place in producing the progesterone after day 120
Fetoplacental unit
What is the fetoplacental unit
Hormones that is produced by the fetus that is released into the placenta producing other hormones in the mare to maintaining pregnancy
Why does a late gestational mare deliver preterm
If there is something wrong w/ either the fetus or the placenta
What is the time line of production for the fetoplacental unit
It activates around 70 days of gestation but isnt effective until around 120 days
When is supplemental progesterone advised
Anytime prior to 120 days of gestation to help pregnancy hormones until the fetoplacental unit takes over
What is the chorion
The dark red side of the allantochorion that connects to the uterus
What is the allantois
The dark purple side of the allantochorion that is the wallpaper to the foal that is very vascular and transfers nutrients/oxygen
What is the amnion
The thin membrane that directly surrounds the fetus
What is the umbilicus
The navel of the fetus that goes thru the allantopic layer
What is the cervical star
Part of the placenta that is attached to the cervix that does not provide any nutrients to the fetus
What type of placenta does horses have
Diffuse
What is epitheliochorial
Nutrients that has to go thru capillaries of the uterus, transfers thru connective tissue, then goes into the chorionic side of the placenta then vise versa
What is neonatal isoerthrolysis
If the experienced dam has a different blood type than the fetus which leads to the dam producing antibodies against the foal that is transferred into the colostrum killing the RBC’s in the foal once they drink the colostrum
What position does the foal get into around 7 months to reduce the risk of dystocia
The foal’s back legs get tucked into each uterine horn
What is the reasons for early embryonic death
Lack of endometrial cup formation, mares that are underweight, mares that are stressed, if there is an error in the development of organ formation/organization
Why is twins undersirable
A single foal needs to be in contact w/ about 70% of the uterus so when there are two foals twins are different sizes due to the differnce in placenta exposure
What does a mares having twins lead too
Late term abortions, still borns, and dismaturity in those that do survive
Why do most twins come out dismatured or worse
Because the type of placena and the size of the uterus the foals are not able to get the appropriate amount of nutrients to survive
When are twins more common in mares
When ovulatory agents are used
How do we manage twins in horses
We monitor for double ovulation and chance it or pinch it
How is pinching done
Before fixation the embryo is squished against the pelives like a grape
What are the other ways twins can be avoided
Abortion of pregnancy, aspiration, cranio-cervical dislocation, and intracardiac injection
What is the only way to remove a twin during late gestation
Using the intracardiac injection
What are the three ultrasounds that are done
The early examination (12d-15d), the heartbeat (25d), and fetal sexing (60d)
What two things are used in rectal palpation
Tone and size of uterus
What are other methods of determining pregnancy
Teasing, blood/urine eCG testing, and measuring hormone levels
During what trimester requires more nutrients for the mare
The third trimester where there is increased stress for the mare due to increased growth
What vaccine prevents viral abortion
Equine herpes virus (EHV 1 sub type B)
What does EHV 1 sub type B due to cause abortions
It attacks the blood supply of the placenta
When do most abortions caused by EHV 1 sub type B
Between 6-10 months
How often does the EHV have to be boosted
Every 60 days
What happens to the BCS of mares during lactation
They will loose 1-1.5 BCS so ideal is a 6-6+
When are the two important time lines for BCS
The last 100 days and early lactation
What causes fescue toxicosis
The ergot alkaloid found in fescue grass
What does fescue grass look like
A stem and the leaves form a collar around the stem
What produces ergot alkaloid
fungal endophyte
What does fescue toxicosis do
It acts as dopamine agonist which inhibits prolactin, vasoconstriction, and decreases estrogen tissue binding
What are the symptoms that arise from fescue toxicosis
Agalactia, placental compromise that leads to dysmature foals, thickend placenta, and lower progesterone levels, and prolonged gestation which causes dystocia
What is the stress hormone that triggers parturition
Fetal cortisol
What prevents fescue toxicosis
Mares are moved from a pastrue setting between 30d-90d and can be given domperidone to conteract the ergot alkaloid
When are pre foaling vaccines given
Around 30d prior to foaling (310d)
What vaccines are given for pre foaling vaccines
Whatever the horse gets as their annual booters
Why are pre foaling vaccines given
So the anitbodies for the diseases become concentrated in the plasma to be transmitted into the colostrum
When should a late gestation mare need to be in their foaling location if it is away from home
At least 30d so she can develop normal microbes found in the environment
What is the caslick
Where the vulva is sown from the anus to about mid vulva to keep bacteria out of the reproductive tract
When is fetal viability
320d
What is the average gestational length
340d-360d
When does heavy monitoring start
Around 310d
What is primiparous
Means that this is their first pregnancy and is a maiden
What is a multiparous
An animal that has multiple pregnancies
Why does dripping milk typically occur w/in hours of foaling
The hormones that induce parturition also induce milk let down
When does the udder typically begin filling
2-6 weeks prior to foaling
When does ligament and muscle relaxation occur
Last few weeks
When does vulva relaxation occur
In the final days prior to gestation
What does pH usually do prior to foaling
It drops typically below a 6
What are red flags to watch when managing pregnant mares
Prolonged streaming, lack of udder development, premature udder development, colic symptoms, brown fetid vulva discharge, large painful abdomen, signs of laminitis, and fever
What fetal hormone controls the time of parturition
Fetal adrenal cortisol
What happens when the fetus goes into stress
Fetal adrenal cortisol increases activating production of placental PGF2 alpha
What does an increase in placental PGF2alpha cause
Uterine contractions causing cervical dilation and the levels peak at the end of stage 1
Why do we typically not check dilation during parturition
Because it could introduce bacteria to the mares repro tract
Why is induction not common in mares
Because it could cause malpresentations, dysmaturity, colostrum problems, etc
What does an increase in oxytocin receptors cause
Increases oxytocin response, uterine contractions, surge w/ ferguson reflex, levels peak during stage 2, and triggers milk let down
What does the allantochorion rupturing represent
Water breaking
What is a red bag delivery
When the allantochorion does not burst and the amnion does not present the chorion does
What is the time line of stage one of parturition
Lasts about 4-6hrs and ends w/ water break
What two main things occur in stage one
The fetus gets into position and there are initial uterine contractions
What is the righting reflex
When the foal is turned on their back and they have an instinct to turn around
What is the tme line for the second stage of parturition
Begins w/ water break and ends w/ foal delivering
How long should stage two last
Less than 30 mins
What is the normal posture for a foal during foaling
The diving position foot foot nose each about 6 ins apart
What is proper presentation for a foal during foaling
Anterior longitudinal or foals head towards the mares vulva
What is the normal position for a foal during foaling
Dorso sacral
What is position
The relationship between the foals back and the mares spine
What is the ferguson reflex
A surge of hormones that stretch the birth canal and increase uterine contractions
How long can progess be delayed before assisting the foaling
5-10 mins
Why should you assist the foaling after 5-10 mins
Because the placenta has already started to detach which does not allow the foal to get the oxygen it needs
What direction should the foal use after the head and shoulders are delivered
Toward the mares hocks
In what breeds are dystocia more common
Thoroughbreds, drafts, and minis
What is malposture
Misplacement of limbs or head the most common dystocia
What is malpresentation
Turned around
What is malposition
Upside down
What are dystocias usually caused by
Large fetus, weak maternal contractions, and exhausted mares
How do you correct dystocia
Assisted vaginal delivery, cesarean section, or fetotomy
After what amount of time does the chances of stillbirth greatly increase in horses
Roughly 30-40 mins
What are the two red flags of stage two of parturition
Dystocia and delayed progess
What is the third stage of parturition
Passing placenta
What is the time line of the third stage of parturition
Starts w/ foal being delivered and ends w/ delivering the placenta
How long should stage three of parturition last
W/ in 3 hours
