المساعد الشخصي الرقمي

مشاهدة النسخة كاملة : Problems of Bovine Pregnancy,


dr_mahmoud61
11-03-2010, 10:18 PM
Elective termination of pregnancy:The indications for elective termination of pregnancy include:
<UL>Inadvertent breeding, such as breeding to the wrong bull, a heifer that was too small when bred, and feedlot heifers;
Pathologic pregnancies such as hydrallantois.
It should be remembered when trying to abort feedlot heifers that if they are receiving a progestin type growth promotant that administration should be stopped while trying to abort them to prevent the CL "rescue" phenomenon.
</UL>Physical methods to terminate pregnancy include rupture of amniotic vesicle before 65 d of gestation.
<UL>The fetal membranes may remain in utero for 2-3 wks after AV rupture.
Decapitation of fetus may be performed, usually between 65 to 90 days. It becomes difficult after 3 mo.
Abortion will occur in 10-14 d, the fetus may mummify.
Intrauterine infusions can result in pregnancy loss.
Enucleation of CL, although practiced in the past, is NOT RECOMMENDED. It may result in hemorrhage (sometimes fatal) and adhesions. It was used before PGF became available.
</UL>Hormonal methods of pregnancy termination
<UL>More common than physical methods.
During normal pregnancy, the CL is required for the first 5 month and the last month of gestation. An extra-gonadal source (placenta) (plus adrenals?) is available during the remainder of gestation.
To terminate pregnancy during the first 5 mo use PGF, during the 6th, 7th and 8th month use PGF plus a corticosteroid (usually dexamethasone).
<UL>If PGF is used alone, there is sometimes incomplete luteolysis and placental progesterone production may rescue the pregnancy.
Corticosteroid alone although it reduces placental secretion of progesterone, does not cause luteolysis until the last month of gestation. The fetoplacental unit must be mature in order for corticosteroids to terminate pregnancy.
During the last month, either PGF or corticosteroid is usually sufficient.
Estrogens were used before PGF was available but in general have poor efficacy. Estrogens are more reliable in the first 5 months, but PGF is more so.
</UL></UL> Induction of parturition:There are a number of indications for induction of parturition. These include:
<UL> 1)health of the cow - either to save her or to save the calf because of the dam's deteriorating condition;
2)prevent dystocia? - induction of parturition has been proposed as a means of reducing dystocia because the calf gains up to 1.0 kg/d near the end of gestation;
3)in dairy cattle parturition may be induced to prevent excessive udder edema from damaging the udder supports;
4)in beef cattle induction of parturition can be used to truncate the calving season, thereby allowing more time postpartum to resume cyclicity before the next breeding season;
5)management considerations, e.g. more efficient use of facilities and manpower;
6)seasonal calving to allow better use of available feeds (more common in New Zealand);
7)allow closer supervision to be able to provide assistance at the earliest indication (especially with valuable animals such as embryo transfer calves).
</UL>There are important criteria to be met for a method to be considered successful. A method should:
<UL> 1)be efficacious,
2)provide a predictable time of delivery,
3)have no adverse effects on the health of the dam,
4)have no adverse effects on the health of the offspring,
5)alter neither the quantity nor quality of colostrum,
6)not affect postpartum involution or subsequent fertility,
7)not increase the incidence of retained placenta.
</UL>Some precautions should be considered for a successful outcome.
<UL>You should have a fairly accurate and reliable breeding date because while calves born up to 2 wks early have normal vigor, those born more than 2 wks premature have reduced viability.
If a large number of animals is to be induced, consider the needs of a large number of calves and husbandry requirements.
</UL>Methods used to induce parturition in cattle: Long acting corticosteroids are insoluble esters or suspensions such as:
<UL>Dexamethasone trimethylacetate (20 mg),
Triamcinolone acetonide (10 mg),
Flumethasone suspension (10 mg),
Betamethasone suspension (20 mg).
These are injected i.m., approximately 1 mo. prior to the due date.
Parturition occurs in 4-26 d. This wide range is a disadvantage in some respects.
Preexisting health conditions in the dam may be exacerbated because of the long acting corticosteroids.
The incidence of retained fetal membranes is low (9-22%) compared to other methods of induction.
However, there is a high incidence of calf mortality (17-45%).
<UL>Calf mortality is due to premature placental separation and uterine inertia.
The calves die in utero and are born partially autolysed with the membranes intact.
Hypogammaglobulinemia is frequent in calves born alive. This is because colostral immunoglobulins are reduced and in addition the calves are often weak and ingest inadequate amounts of colostrum.
</UL></UL>Short acting corticosteroids are soluble esters such as:
<UL>Dexamethasone (20-30 mg),
Flumethasone (8-10 mg),
Betamethasone (30 mg).
They are generally efficacious (80-100%).
They can be injected i.m. within 2 wks of the due date.
Parturition usually occurs in 24 to 72 h, with an average of 48 h.
There is no increase in calf mortality if used within 2 wks of term. Earlier than this there is the risk of inducing a premature calf.
Colostral immunoglobulins are normal.
The major disadvantage is an increased incidence of retained fetal membranes.
<UL>The likelihood of retained fetal membranes is related to the degree of prematurity and ranges from 30 to 100%.
The earlier parturition is induced, the higher the percent of retained fetal membranes.
</UL></UL>Prostaglandins : Drugs available at this time in the US include:
<UL>Prostaglandin F2a (25 mg),
Cloprostenol ( 500 ug),
Fenprostalene (1 mg).
They are similar to short acting corticosteroids as far as efficacy, time from administration to expected calving, incidence of retained placentas, etc.
They have no great advantage over corticosteroids.
</UL>Estrogens: These are generally considered an "old" method, used before prostaglandins were available. They have relatively poor efficacy (60-80%). They also have a high incidence of retained placentas.
Combinations:
<UL>Combining short acting corticosteroids and estrogens does not decrease the incidence of retained fetal membranes. Large doses of estrogens decreases the interval to parturition by several hours and reduces induction failures.
If long acting corticosteroids are followed by short acting corticosteroids or prostaglandins 7-12 d later, most cows will calve 2-3 d after the second injection. The interval is shorter and more predictable with PGF, however, the incidence of calf mortality is still high.
Using a combination of corticosteroid plus prostaglandin does not decrease the percent of retained fetal membranes. However, there are fewer induction failures, but there is no real advantage.
</UL>Problems of pregnancy
Dropsy conditions include hydrallantois and hydramnios. Hydroallantois, or hydrops of the allantois, is due to a defective placenta (the chorio-allantois).
<UL>The fetus is normal.
The condition is characterized by a rapid accumulation of watery, clear fluid, usually in the last trimester.
The cow is rounded in the caudal view, and you normally can't palpate the fetus or placentomes.
</UL>
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/HY-ALL-1.JPG <UL>Usually the condition results in a sick cow with anorexia, decreased rumen motility, dehydration and weakness.
The cow may be down.
The placenta is thick.
If the cow survives, postpartum metritis is common.
The condition usually ends in death or intervention.
The prognosis is guarded to poor for life and fertility.
Treatment consists of Caesarian section with a slow drainage of fluid and perioperative support.
Dexamethasone can be used if the cow is not down.
</UL>http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/HY-ALL2.JPG
Hydramnios, or hydrops amnios, is due to a defective calf, usually attributed at least partly to a defect in swallowing.
<UL>The placenta is normal.
The condition is characterized by a gradual accumulation of thick, viscid fluid during the last half of gestation.
The cow has a pear shaped caudal view.
Usually you can palpate the fetus and placentomes.
The cow is clinically otherwise unaffected.
The pregnancy usually goes to term, and frequently a small, deformed fetus is delivered.
Postpartum metritis is uncommon.
The prognosis is good for life and fertility.
No treatment is required.
The cow may be allowed to go to term or induced to calve.
</UL>


Uterine torsion
Uterine torsion usually occurs near term and is usually found at parturition because of the subsequent dystocia.
The attachments of uterus and manner in which cows rise are assumed to play a role in the development of this condition.
Diagnosis can be made by a number of ways.
<UL>By manual vaginal exam, the vaginal wall can be felt to be twisted or spiraled. This can be visualized with the aid of a speculum.
By rectal exam, the broad ligaments can be felt to be crossed and the uterus twisted. The vulva can often be seen to have a slight twist of the dorsal portion.
</UL>It is important to determine the direction of the torsion during the examination.
When correcting a dystocia, if the calf is found upside down (dorso-pubic), consider the possibility of a uterine torsion.
Before and during correction, insure that things are going in the proper direction.
If the cervix is open, a detorsion rod may be used.
Alternatively, the torsion may be corrected manually by rocking the fetus until enough momentum is achieved to flip the uterus.
If the cervix is closed other methods must be employed such as the "Plank in flank" method or surgical (C-section) correction.
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%201.gifhttp://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%202.psd.gif http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%203.psd.gif
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%204.psd.gifhttp://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%205.psd.gif
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/pnf%206.psd.gif





Uterine Prolapse
Lay terms for this condition include "cast her wethers" and "lost her calf bed". This is a true emergency. This is an acute condition that is often associated with hypocalcemia and may also follow use of great force in fetal extraction. It is not hereditary.
Diagnosis is fairly obvious, caruncles can be observed on the uterus which is prolapsed through the vulva. The prolapse can involve other organs such as the bladder or intestines. In some cases, the uterine artery may rupture with fatal consequences.
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cow%20prolapse009.jpg
The prognosis is relatively good if the uterus does not suffer too much trauma and is replaced properly. The chance of recurrence not great. If properly corrected, there are no serious long term effects, although there may be a slight increase in days open during that lactation.
Correction isaccomplishedbyfirstcleaning the uterus to remove dirt and accumulated debris.
<UL>Proper restraint is essential.
Epidural anesthesia is helpful to prevent straining.
To aid in replacing the uterus, tip the pelvis cranially by placing the cow in a "frog leg" position and elevate the uterus (either by elevating the hind quarters of the cow or having assistants hold the uterus up).
It may help to empty the bladder if it is trapped.
Generally the placenta is removed only if loose.
More trauma is caused to the endometrium by manually removing the placenta than by leaving some attached to the uterus.
Sugar or other such substances are sometimes used in an attempt to reduce the edema in the uterus and shrink it down. However, the effect is not remarkable.
Oxytetracycline powder or other broad spectrum antibiotics are sprinkled on the uterus before replacement or placed in the uterus after replacement.
Completereplacement is essential to prevent continued straining and reoccurrence.
Some recommend suturing the vulva after replacement with heavy suture material in something like a large horizontal pattern. Although this is often done, it is considered a placebo procedure if the uterus has been properly replaced.
Oxytocin should be given after replacement. If given before replacement, the uterus will contract down and make the job more difficult.
It is important to treat milk fever first before replacement because that is a more life threatening condition.
Hysterectomy is considered a salvage procedure.
</UL>http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cows001.jpg



Vaginal prolapse


This is often a chronic condition and is hereditary.
There is a breed predisposition with Hereford, Santa Gertrudis being predisposed.
Vaginal prolapses often recur. For this reason, it is recommended to cull cattle with a vaginal prolapse.
They usually occur prepartum, in late gestation, when the cow is under the influence of rising estrogen and experiencing relaxation of the tissues.
They may occur postpartum or may be associated with follicular cysts.
Upon presentation, the vagina, with or without the cervix, is seen protruding from the vulva.
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cows006.jpg
The tissue is often dry and necrotic.
Tenesmus is common.
When considering the prognosis, although rarely life threatening, consider the chance of recurrence and inheritance and recommend culling.
These are much easier to replace but harder to maintain in the correct position.
Correction is aided and tenesmus reduced with an epidural.
<UL>The tissue is cleaned,, lubricated and replaced.
After replacing the prolapse, the cow may be maintained so that her hind quarters are elevated (dairy cow)
These need to be sutured to help reduce the risk of reoccurrence.
There are numerous methods of fixation.
<UL>Probably one of the most effective is the Bühner stitch.
<UL>This requires a Bühner needle and Bühner tape. If other material such as umbilical tape is used, results are unsatisfactory. Umbilical tape, for example, will break and also wicks bacteria.
</UL>http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cows004.jpg

<UL>The Bühner stitch must be removed prior to parturition.
</UL>Minchev's technique is useful prepartum, especially in cattle that cannot be watched closely because they are able to calve with the Minchev buttons in place.
</UL>
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cows002.jpg <UL>Tissue trauma, swelling and inflammation may be a problem.
</UL><UL>Other techniques commonly used include:
<UL>The "boot-lace", where eyelets are made from hog rings or sutures. This can be removed temporarily and replaced by lay help, for example in prepartum cases.
</UL>http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cows005.jpg

<UL>Modified Caslick's are also used occasionally with varying degrees of success.
Pessaries are also used occasionally with varying degrees of success.
Trusses, etc. are also used occasionally with varying degrees of success.
</UL></UL></UL>

Fetal mummification

This occurs in cases of fetal death without involution of the corpus luteum and fetal expulsion, followed by autolytic changes, absorption of the fetal fluids and involution of the placenta.
In cows the maternal caruncle involutes and hemorrhage occurs between the placenta and the endometrium, leaving a reddish-brown, gummy mass that imparts a reddish brown color to the mummified fetus.
The etiology is varied and ranges from infectious causes such as BVD, leptospirosis, etc. to non-infectious causes such as genetic, compressed umbilical cord, etc.
Diagnosis is based on the presence of a CL, the lack of fremitus in the uterine artery and lack of fetal fluid in the uterus. The fetus feels dry and mummy-like on palpation. Oftentimes the head, ribs, etc. can be felt.
Prognosis is good if the fetus is removed. After the fetus is removed, conception usually occurs 1-3 mo. later.
Treatment is accomplished by administering PGF2a (with or without estrogen) to lyse the CL. Steroids are ineffective with dead fetus and non-functioning placenta. After treatment, check the vagina because sometimes the mummy may be lodged in the vagina when expelled.
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/BOV-MUM1.JPG
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/BOV-MUM4.JPG



Fetal Maceration
Fetal maceration results from death of the fetus followed by dilation of the cervix and incomplete abortion or dystocia, usually during the last half of gestation. This condition can be due to a variety of miscellaneous organisms.
Diagnosis On palpation per rectum, the uterine wall is thick, little or no fluid is present in the uterus and you may be able to palpate fetal bones and pus, or bones crepitating against each other in the uterus.
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/BOV-MACER1.JPG
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/BOV-MACER3.JPG
Prognosis The prognosis is poor for cows with this condition. This is not a "retained CL" problem so lysis of the Cl is not helpful. Endometrial damage is present even if all fetal parts are removed.
Treatment Treatment is very difficult. The cervix cannot usually be dilated sufficiently to remove all the fetal parts and any remaining fetal parts act as an IUD. Surgery has been performed in valuable individuals but is very difficult.


Calving Injuries

Postpartum hemorrhage: This can be due to a variety of causes. When observed, the origin of the blood should first be determined.
Lacerations or tears are usually due to mishandling during OB procedures.
Tears in the uterus are usually located in dorsally, near the cervix. They can be diagnosed by palpation or visually.
<UL>(Sideline: Schistosomus reflexus should be included in the differential diagnosis when viscera are observed protruding from the vulva or palpable during an obstetrical procedure.
</UL>
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/bov-schist.tif.jpg <UL>This is a congenital defect where the spine is bent back on itself in a hairpin turn and the ventral body wall is not closed.
This defect is incompatible with life although the calf may be alive at the time of attempted delivery.
Delivery requires a fetotomy or cesarian section.)
</UL>http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/SCHIST-2.JPG
http://www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/SCHIST-1.JPG
<UL>The prognosis in the case of lacerations of the reproductive tract varies with the location and extent of the tear.
Peritonitis is a possible sequela.
Small tears may heal without treatment.
Larger ones should be sutured, either via laparotomy (difficult) or by intentionally prolapsing the uterus. This can reportedly be achieved by administering 10 cc epinephrine i.v., but is not effective after oxytocin administration.
</UL>Cervical tears can result in profuse bleeding. Not as critical to future fertility as in the mare but may reduce fertility depending on the extent. No real treatment, rather try to prevent.
Vaginal tears are not uncommon. They may go unnoticed unless they result in hemorrhage.
<UL>There are large arteries at the 1:00-2:00 and 10:00-11:00 positions.
Otherwise, a vaginal tear may be noticed because of masses of fat protruding from the vulva after calving or during a vaginal exam.
During the postpartum period they may be suspected during a rectal exam when hard masses are palpated in the vaginal area.
Again, the prognosis varies, depending on the location and extent.
If significant hemorrhage is occurring, place a pair of hemostats on the artery for 24 h.
Attempting to suture the artery is difficult.
After 24 h, the hemostats may be removed and the hemorrhage will have stopped.
</UL>Vulvar or perineal lacerations can be sutured immediately if seen at parturition, otherwise wait until all the swelling, inflammation, etc. is gone.
A laceration in the vaginal or vestibular areas may sometimes become an abcess. They should be allowed to heal. Many times no treatment is needed, especially if the dam is not systemically ill. Caution should be exercised to not transport infective material into uterus during anytreatments. (For example - a cow is found to have a foul smelling vaginal discharge but the uterus is normal on rectal palpation. A vaginal exam should be performed because if the source is a vaginal tear or abcess, treating the uterus would drag the infective material into the uterus.)
Caruncles, if torn during obstetrical procedures can be the cause of observed hemorrhage. Usually no treatment is needed.
The umbilical cord will result in bleeding after it ruptures. This is normal but if significant hemmorhage is observed, you should verify that the ruptured cord is the source and there are no tears.