Solving the Mysteries of Obstetrics, Part 3 of 5
Special Problems During Pregnancy
Goats are multiparous, meaning they normally have multiples in the litter. Superfecundation means that two different sires are fathers of different individuals in the litter. Offspring are either from one sire or the other, not a combination of the two. It is impossible to determine parentage solely by the offspring's appearance. Your breed association is the ultimate authority on paternity questions when more that one sire serves the same doe on the same heat period. It may be preferable to terminate accidental pregnancies early, so you can breed the doe again and not waste a breeding season.
This is quite rare. A bred doe may come into estrus, usually at the heat period following conception, and conceive additional offspring. Any additional embryos are carried with the already-established pregnancy. The fetuses conceived on the first cycle are sometimes delivered, and the second part of the litter is delivered three weeks later (assuming normal heat periods). Or premature fetuses can be delivered along with full term fetuses. There are documented cases of "embryonic diapause" in sows 1, and anecdotal cases in goats and sheep. Diapause means that some fetuses are held in reserve and are delivered at 2 weeks or more apart from the first litter. When does are bred on multiple heat cycles, it may appear that superfetation has occurred due to fetal sizes and maturity differences. Abortion of one or more fetuses while others are carried to term may also be confused with this condition. Do not mistake this with a still-pregnant female who adopts the kids of a herd mate who kidded unobserved.
Early Fetal Losses
There are numerous reports about embryonic loss in ruminants. Embryonic losses are resorbed, as opposed to aborting. Between 25% to 40% of pregnancies are lost in cattle and sheep within the first 4 weeks of pregnancy due to a variety of causes.4 In people, 75% of all fetal loss is believed to be caused by genetic abnormalities. On the farm it is nearly impossible to determine the cause and time of embryonic mortality. Coming into heat at the next estrus period after breeding (3 weeks in goats) may be due to early embryonic mortality or conception failure. When a doe skips a heat cycle, 6 weeks from estrus to estrus, she probably conceived and sloughed the embryo(s). The doe may also act and appear pregnant for up to three months and return to estrus, indicating a failure of early pregnancy. If this occurs twice when a doe is bred to the same buck, change to an unrelated sire. If it happens to more than one doe, especially related does in the same breeding season, change to an unrelated sire. Two or three instances of this cause a doe to miss a whole breeding year.
Factors Involved in Embryonic Mortality
There is a difference between abortion (dead fetus) and early delivery (dead or live), although it can be difficult to tell the difference, especially without a firm breeding date. Abortion can be due to infectious or non-infectious causes. Each abortion should be medically investigated by sending the aborted fetus and placenta to a diagnostic lab to see if an infectious organism can be found. Non-infectious abortions may be due to: chemicals, drugs, toxic plants, hormone aberrations, administration of hormones, malnutrition, genetic or chromosomal abnormalities, trauma, excessive stress, fever, surgery and a few more obscure causes. A survey of aborted livestock fetuses, stillbirths and neonatal deaths shows that 8.7% were due to congenital defects. Related reading: Abortion
Documentation regarding birth defects in goats is scarce. It has been postulated that livestock probably have the same incidence and types of defects as humans. Some birth defects which distort the fetus can cause dystocia. The next article, Chart of Genetic Defects, lists those known to affect ruminant livestock and which ones contribute to dystocia. Some plants, chemicals and drugs can cause birth defects, and the severity of the defect of an organ or system often depends on when the toxicity occurs during gestation.
Resorption usually occurs when fetal death occurs before bones begin to form. After bones begin to form, a dead fetus may mummify when a viable fetus is present. If the pregnancy is carried to term, the mummy may be passed or create dystocia.
Soft tissues of the fetus decay. Bones may be passed or retained. All bones must be removed from the uterus to prevent infection and/or injury.
As discussed in Part 1, there are two fetal membranes, the amnion and allantois, either of which may accumulate excess fluid. The incidence of hydrops in cattle is estimated at 1 in 7500 pregnancies. Hydrops of either membrane is characterized by excessive abdominal enlargement. It is often associated with fetal abnormality, i.e. cleft palate or pituitary hypoplasia. Delivery assistance is usually required because of uterine inertia due to over-stretching. Hydrops allantois, the more life-threatening of the two conditions, has been reported to affect the same cow twice, and it may have a genetic component.
Uterine Rupture During Pregnancy
Accidents are thought to be the primary cause, but it may be due to other factors. This has occurred in a Pygmy doe at 4 1/2 months pregnant who carried to term. At birth, cervical dilation was partial and uterine contractions were absent. During C-section variable amounts of fibrinogen are found in the abdominal cavity.
Some factors predisposing to prolapse include: breed, genetic predisposition, high levels of estrogenic feeds and ageing. In Pygmies, this is probably more commonly due to fat body condition with multiple fetuses, especially in shorter-bodied does, and perhaps genetics. A doe with a prolapse may prolapse earlier in her next pregnancy. Intra-abdominal pressure forces the vagina through the vulva. At first the prolapse is intermittent and disappears when the doe stands. The prolapse worsens as the doe strains due to irritation of the delicate tissue. It is very important to prevent tissue damage. Sometimes a rectal prolapse will accompany a vaginal prolapse due to straining and intra-abdominal pressure. It is often necessary to have a veterinarian place sutures to contain the prolapse(s). The owner must be present at birth to remove the sutures or the doe will be injured and the litter may not be delivered.
Pregnancy Toxemia (Ketosis)
This is caused by an energy deficit in late gestation or early lactation. Excess body fat can be a contributing factor due to fatty liver disease and because abdominal space-occupying fat prevents the doe from eating enough. It can also occur in females in very poor body condition and in those carrying multiple fetuses. Signs of ketosis are anorexia (off feed), lethargy and pain. Caught early, ketosis can be treated with propylene glycol given orally. Excess ketones in the urine may be detected with test strips available at the drug store.
Mistakes in breeding dates and figuring gestation length are often misinterpreted as abnormally long gestation. Normal gestation in goats ranges from 144 to 155 days, and prolonged gestation is longer than 155 days. True prolonged gestation may be due fetal pituitary aplasia or fetal death. Record breeding dates and use a reliable gestation calendar.
Vaginal Discharge During Pregnancy
This may be normal or indicate a vaginal or uterine disease process or abortion. If the discharge appears to be what the doe normally passes when she is in estrus, and if she acts normally, it is probably normal. Blood-stained, brownish or foul-smelling discharges are abnormal.
Congenital Defects & Fetal Monsters
Up to 3% of all calves and 2% of lambs are born with birth defects. Of these, 40% to 50% are stillborn, and most physical defects are visible. Without accurate statistics we can probably assume that the same is true in goats. According to body system involved, the percentages are: 55.4% musculoskeletal, 12.7% digestive, 9.7% cardiovascular, 8.0% urogenital, 6.0% central nervous system, 3.5% special senses, 3.2% skin, 1.5% endocrine. Recessive autosomal genes (non-sex trait genes) are responsible for between 50% to 63% of hereditary abnormalities. Sex trait gene defects appear to occur about 0.6% of the time (about 1 in 160), except in the case of polledness in goats which is about 25%.
References used in this series of five articles:
1. Jackson, P.G.G. (1993) Handbook of Veterinary Obstetrics
2. Morrow, David A. (1986) Current Therapy in Theriogenology
3. Bogart, Ralph (circa 1960) Principles of Animal Breeding
4. Hafez, E.S.E. (1993) Reproduction in Farm Animals
5. Dennis, Stanley M., editor (1993) Congenital Abnormalities,
The Veterinary Clinics of North America, Food Animal Practice
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