Equine Reproduction

 

 

Lesson 7

 

 

Fetal Development, Abortion, Induced Parturition and Dystocia in the Mare

 

 

 

Assignment: Read Chapter 8 & 10 in the text.

In this lesson we will revisit specific embryonic and fetal ages that are significant in the overall management concerns of a breeding farm. These time periods should be committed to memory.  They are listed as items A through K under I, below.

 

 

I.             Normal fetal development in the mare

 

A.   Fertilization of ovum (egg) occurs in the oviduct (fallopian tube) of the mare.

 

B.   Fertilized ovum transported into the horn of the uterus at 5 to 6 days.

 

C.   Recovery of embryo at 7 days for embryo transfer is 64 to 128 cells.

 

D.  Day 14 embryo prevents release of prostaglandin and can be detected by ultrasound as a pregnancy.

 

E.   If twinning has occurred, pinching off one vesicle (embryo) is attempted at approximately day 18 when the embryo has fixed in location.

 

F.   Endometrial Cups form by day 45 and release progesterone for pregnancy maintenance until day 120.

 

G.  By day 60 the fetus has the unmistakable appearance of an equine.

 

H.  By days 150 to 160 ears will appear fully developed. Ergots will appear.

 

I.     By 220 days development of mane and tail; the weight will be 8 to 10 kilograms (22 lbs).

 

J.   By day 300 the fetus will have a full hair coat; the weight will be 20 Kilos (44 lbs).

 

K.   By 340 days the weight will reach 45 to 50 kilos (100 lbs).

 

 

 

II.           Abortion in the mare (spontaneous loss of pregnancy before term – miscarriage)

 

A. Early embryonic death – death and resorption of embryo prior to 40

    days pregnancy is very commonly seen on breeding farm (12%

    occurrence).

 

1.   Twinning will often cause a mare to abort at anytime during pregnancy.

 

a. Light breed mares rarely carry twins to term.

 

2.   Infectious causes of abortion.

a.  Equine Rhinopneumonitis virus

1. Can be vaccinated to prevent abortion (pneumabort vaccine – 5th , 7th and 9th month of pregnancy).

 

http://www.fortdodge.com.mx/imagenes_prod/PNEUMABORT.JPG

 

http://www.equine-reproduction.com/articles/abfetus.jpg

 

B.   Equine Arteritis

1.   Not as common as Rhino (presently eradicated from major breeding states).

 

2.   Vaccine available.

              C. Bacterial causes of abortion.

  1. The same bacteria that cause endometritis. Infection is

      not cleared and mare becomes pregnant. Fetus

      becomes infected in the womb, dies and is aborted.

 

 

On occasion it is considered necessary or at least helpful if a mare can be induced to foal at a specific time. When induction of foaling is contemplated it is very important to follow certain guidelines in order to prevent possible complications that may lead to the death of the mare or foal. The following guidelines should be kept in mind when considering induction.

 

III.         Induced parturition

 

A.   Mare must be at full term and show all signs of impending foaling.

1.  Musculature relaxation of croup, buttocks and perineum.

2.  Waxing or milk from the udder.

 

http://rockin-g-ranch.com/Classy_waxing.JPG

 

B.   Veterinarian must be involved.

1.  Check for cervix relaxation of dilation.

2.  Check for correct positioning of the foal.

C.   Procedure.

1.  Mare is prepared for foaling (tail wrapped and cleaned).

2.  Mare is administered Oxytocin (3½ cc) intramuscularly.

3.  Mare will begin first stage of labor within 10 to 15 minutes

     and continue through the normal foaling process.

 

 

 

 

http://web.vet.cornell.edu/CVM/HANDOUTS/plants/Foaling%20normal%20amnion.JPG

Induction of parturition can occasionally be accompanied by complications, so attendance by veterinarian is crucial.

 

 

 

IV.         Problems involving normal delivery.

 

The following should supplement your text reading and can be used as a study guide for common foaling problems that may be encountered.  This material does not prepare the student for dealing with foaling problems without the attendance of a veterinarian.  Time is of the essence when the mare is in distress – call the vet immediately. 

 

A. Red Bag Delivery (premature placental detachment).

If reddish membrane appears before the foal appears, it is an emergency and the bag must be torn open and the foal must be pulled as quickly as possible (the blood supply to the foal is separating too early).  Those attending the mare must act quickly – in this instance waiting for the veterinarian will ensure death of the foal – be prepared. 

 

http://web.vet.cornell.edu/CVM/HANDOUTS/plants/Foaling%20redbag.JPG

Red Bag Delivery

 

B.  Dystocia – Difficulty in foaling usually do to malposition of foal.

 

1.  Breech birth – hind legs come first – not commonly seen – you must deliver foal as soon as possible (cord may break before the head is cleared from passage, preventing normal breathing).

 

2.  There are many other types of malposition of foal, some can easily be corrected and some may require cesarean section.

 

 

http://www.twhbea.com/062568D6007A2B8A/Files/Foaling3/$file/Foaling3.gifhttp://www.twhbea.com/062568D6007A2B8A/Files/Foaling2/$file/Foaling2.gif

 

          If foal is not delivered within 30 to 40 minutes of the beginning of the second stage of labor (after the water breaks) there will be a much greater chance the foal will be born dead.

 

C.  Uterine Torsion

1. This is a twisting of the uterus in the cervix area, and can

    occur anytime during the last few months of pregnancy.

 

2. Veterinary attention is necessary as soon as possible,

    sometimes surgery is indicated.

 

D.  Uterine Prolapse

1. This occurs shortly after the foals is born. Uterine

    contractions to expel the afterbirth may cause the

    uterus to prolapse or come out of the abdominal cavity.

 

2. This is an emergency requiring veterinary assistance

    as soon as possible.

 

E.  Uterine Rupture

1. Mare will stop passing foal and go into shock.  You should

    pull the foal; if already partially passed (head is out) the foal

    will probably survive.

 

  This is an emergency that requires immediate 

  veterinary assistance; the mare may not survive.

 

F.  Ruptured Uterine Artery

1. Mare usually bleeds out within 5 to 10 minutes causing

    death.

 

2. Most often seen in older mares (over 15 years of age).

 

 

V.           Complications in mare following delivery.

A. Internal hemorrhage.

1.    Uterine bleeding can be severe or mild.

 

      a. Vaginal lacerations – seen with large foals. 

 

           b. Cervical lacerations – usually cause minimal

                bleeding.

 

 

B. Retained Placenta.

1.  Considered retained after 3 hours.

2.  Do not pull on afterbirth; do not tear afterbirth.

a.    Requires veterinary assistance.

1.   Oxytocin injection to stimulate uterine contraction.

 

2.   Intrauterine antibiotic infusions.

 

3.   Infection caused by even small pieces of afterbirth can cause shock and founder in the mare.

 

http://www.horsecity.com/images/011402/Placenta.jpg

 

 

        C.  Cramping or signs of colic after foaling.

                           1. Usually due to uterine contractions post foaling.

 

                           2. Banamine or Bute should not be used unless the mare

                               has already passed her afterbirth (will inhibit uterine

                               contractions).

 

                           3.  Some post foaling mares are more apt to have impactions

                                post foaling. Mineral oil given by the veterinarian would be

                                indicated

 

 

D. Perineal Lacerations

                           1.  Normally caused by large foal.

 

                           2.  Normally should be immediately attended to by

                                veterinarian (sutured).

 

 E. Rectovaginal lacerations

                            1.  Caused by foals foot being driven through the vaginal

                                 wall into the rectum during  a uterine contraction while

                                 foaling.

 

                            2.  May just leave a hole through this area if foals foot

                                 is replaced before more contractions occur

 

                     F.  Third degree RV laceration refers to the shelf between the

                          rectum and vagina being completely torn out.

 

                            1. This is not normally an emergency.

 

                             2.  Veterinarian usually not able to suture the laceration

                                   immediately due to the extensive bruising of the tissues.

 

                              3.  Mare is put on antibiotics, given a tetanus injection,

                                   given pain medication and allowed to heal as is for

                                   about 3 weeks to 2 months before veterinarian will

                                   consider stitching the area.

 

                               4.  Must keep mare as clean as possible and treat the

                                     wound regularly for optimum healing.

 

                               5.  The surgery to stitch this area is done in the standing

                                    position normally under local anesthetic.

 

 

http://www.ul.ie/~equines/Lecture%201920_files/image004.jpg

Ruptured pre-pubic tendon – can occur in the third trimester of

pregnancy or just before foaling.

 

 

Click here to take Quiz

 

ASSIGNMENT:

Please send to jsales@horsecoursesonline.com     "Lesson 7 Repro" in subject line. 

 

1. In your own words outline the fetal development of the foal from conception to birth.

 

2.  List signs of embryonic loss in the mare and discuss methods that can be used to confirm it.

 

3. What control procedures can be used for those causes of abortion listed in question 2?

 

4. Describe 5 of the more common foaling and post foaling complications and a brief description of proper handling.

 

5. Give at least 3 reasons why twins should not be allowed to go to full term.