In horses, twin fetuses are uncommon. Carrying them to term is even more unusual, and birthing healthy twin foals is especially unlikely. “Twin pregnancies are extremely undesirable in horses, as they almost always have a bad outcome,” said Dr.
Mares that are allowed to carry twin pregnancies are likely to suffer complications as a result. They frequently abort twins or if they give birth to live twins the mares are more likely to suffer dystocia (foaling difficulties), retained foetal membranes and decreased live foaling rates in the following season.
Although pregnancies can be diagnosed with ultrasound as early as 9 days after ovulation, twin pregnancies are optimally detected between Days 13 and 15 of gestation when the embryonic vesicles are still mobile and two embryonic vesicles can be imaged.
While animals of many species routinely give birth to multiple healthy offspring from one pregnancy, horses are not designed to nourish two fetuses and produce viable twin foals. Double pregnancies put the mare and both foals at risk, and good outcomes are rare.
It is important that another ultrasound exam is performed before day 35, ideally on day 28. This allows for the identification of any twin pregnancies that may have been missed at the initial scan. This can occasionally occur as the mare has the ability to ovulate up to 5 days apart and conceive more than once.
The chances of twin foals being born alive are considered one in 10,000. But the odds of both animals surviving past their first two weeks are deemed much higher still, with most pregnancies ending in the death of at least one of the infants and often imperilling the mother.
The survival of healthy twin foals is rare. The fact that Mona carried her twin foals nearly to term, and that they each were about the same size, is even more unusual. Twins historically are the single most important cause of pregnancy loss and abortion in mares, said Dr.
If twins are detected, it is important to reduce the pregnancy to a singleton as soon as possible to increase the chances of a successful outcome. This can be done by manually crushing one of the embryos or using a technique called transvaginal aspiration.
Horses produce only one foal from an eleven-month gestation period, making the maintenance of high reproductive rates essential. Genetic bottlenecks and inbreeding can increase the frequency of deleterious variants, resulting in reduced reproductive levels in a population.
An 11-year-old American Buckskin mare gave birth to live triplets unattended at approximately 300 days gestation. All foals were small and dysmature, requiring intensive care.
Twinning in mares is very undesirable because of low survival rates, usually very weak foals, and numerous conformational problems. Of all twin pregnancies, 60% will birth a live single foal, 31% will abort both foals, and 9% will carry both twins to term.
Generally, assuming a filly is healthy and on a good plan of nutrition, she can be bred as early as two years of age, although many breeders suggest waiting until three years of age. Mares can continue to produce foals well into their late teens or early to mid 20's.
This is called false pregnancy. There are a number of other terms that are used to describe false pregnancy in the mare. They include prolonged luteal activity, persistence of the corpus luteum, prolonged luteal phase, prolonged diestrus, pseudopregnancy, pseudocyesis, and spurious pregnancy.
Taken for instance a horse semen with a human. The pregnancy would not survive. The sperm and egg of different species are incompatible. Technically a pregnancy may begin, but will soon spontaneously terminate.
Technically speaking, fillies usually attain sexual maturity at 12 to 15 months of age, but some reach puberty as early as 9 to 10 months and others as late as 18 months.
Foals that survive are often premature or very weak at birth, and need extra veterinary care and constant monitoring for at least the first week of life. There seems to be a genetic predisposition for twins in certain bloodlines, and it is important for breeders to be aware of this when selecting broodmares.
Some horse breeders have been known to deliberately breed full siblings and/or a stallion to his daughters or his dam as a means of progeny testing in order to manage their breeding selections in the future.
In horses, only one breed, the Clydesdale, has an average level of inbreeding exceeding 25% (top, red line), whereas in comparision, about 75% of dog breeds were greater than 25%. Inbreeding is less than 12.5% (yellow) in about half of the horse breeds, while only a handful of dogs are this low.
Inbreeding is the mating of horses that are more closely related than the average of the population. This includes the mating of brothers and sisters. Linebreeding is a less intense form of inbreeding that is designed to keep a higher relationship or number of genes in the pedigree of the individual someone linebreeds.
Twinning is the most common manifestation of multiple pregnancy in the mare and considered undesirable due to its negative impact on reproduction. Triplet pregnancy is exceedingly rare (Whitwell 1984) and is reported to occur at an incidence of 1 to 300,000 single births (Roberts 1986).
A mare (or female horse) can typically produce one viable foal per year. A mare is capable of producing a foal at about 18 months of age, but it's healthier if the mare is at least 4 years old, as she will have reached her full size. A mare may continue to have foals until she is in her late 20s.
We have had many discussions about this subject at my barn and are still divided on the answer. A: Mares in late pregnancy will occasionally show signs of heat, such as elevation of the tail, frequent urination, and “winking” of the lips of the vulva.
Some mare suffering from placentitis show no external signs and simply deliver a premature or dead foal. Mares that have suffered from placentitis during one pregnancy are at a significantly higher risk of the condition occurring again in subsequent pregnancies.
Prolonged deliveries result in reduced oxygen to the foal, poor doing once the foal is born and potential death. Fetuses may also die due to malformations such as heart defects. Conditions that specifically affect the fetal membranes deprive the fetus of oxygen.
Foals are born with their eyes open. The pupils are initially round to oval in shape and become more horizontal at three to five days postpartum with a lighter-colored iris than adult horses.