Artificial Insemination. The mare.

Introduction
When it comes to rabbits and humans, it is a known fact that the vast majority of them reproduces without medical intervention. Considering the dramatic increase in the veterinary assistance being given to breeding mares in becoming pregnant, it would almost seem as if no horse could become pregnant without such intervention. Nothing, however, is farther from the truth. Historically, for example, we know that the huge herds of wild mustangs, some of which still populate the American west, descend from only a few animals that escaped from the ones the Spaniards had brought with them to conquer Mexico. Proof, then, that horses don't need veterinary help to reproduce.

The reasons why consulting a veterinary is becoming increasingly more common certainly have nothing to do with a charitable attempt to keep me and my fellow veterinaries employed. The real reasons, however, include the following:

Semen is expensive. The vast majority of the male horses in Europe has been gelded or is not being used for breeding purposes. The remaining stallions, then, must service many mares. Since a stallion produces, only a certain amount of semen, this is a limited and costly item.
The circumstances under which horses are kept are a far cry from the horse's natural habitat. Most mare owners are not at all involved in the emotional or sexual drives of their mares, whilst the conditions under which horses are kept are usually far from natural. Often, a mare is dropped off at the stallion managers location with the only message being, "Good luck", or "Call me when she's in foal". So that's what the stallion manager and his veterinary are faced with -and it's a situation that sometimes has its little surprise-. It can even happen that the mare being brought in to be served can be well along in a pregnancy resulting from being served during the previous season.
Costs for keeping horses in general arc high. Since expenses involved in keeping a breeding mare and paying for stud fees are increasing a bit all the time, the pressure 'to perform' is increasing as well. The veterinary is more commonly called in, therefore, 'just to make sure'. In any event, testing for pregnancy has become much more common than it was roughly 10 years ago.

A successful conception involves three requirements:

A healthy mare
A healthy stallion
Effective management

In other words, a natural cover or insemination requires a sufficiently high amount of semen and must take place at the best possible time. That's about all there is to it. It is sad but true that just as in many human cultures, the failure to become pregnant is usually blamed on the female. Stallion managers too frequently assume that their stallion is blameless and that their management has been impeccable, This means that the veterinary is usually called in to look at the mare.

The choice of a stallion is almost never based on his fertility tests. The stallions most in demand for breeding are the ones who perform best in the ring. And when this happens, the availability or the quality of his semen is sometimes not what it should be. The solution might seem obvious: select a stallion that is not so much in demand or is not as old, This choice, however, is up to you. I cannot advise in these matters. Neither can I say much in regard to any problems your own mare might have; you have your own veterinary for this. All the more reason, therefore, for me to discuss the biological functioning of your own mare and that of the stallion you have selected, and what you might be able to do to improve your chances of success, in other words, the management of your one mare or of your entire stud farm.

Next, I will address what can and cannot be done in the way of veterinary intervention. After all, we are not miracle -workers. By understanding your own horse better, you can do a great deal to contributing to the success of your breeding program.

The mare
Breeding mares that are being taken to be served usually undergo routine testing by a veterinary for several reasons. Calling in the veterinary is no longer limited to when a mare fails to become pregnant. This routine testing focuses on determining the right timing for servicing and on checking for pregnancy.

Sound reasons for routine testing include the following:

The stallion will not have to be used more than is necessary.
The amount of semen used (whether shipped or frozen) can be minimized;
The number of covers (and thus the mare's risk of infection) will be minimized.

Poor reasons:

The stallion manager is too busy.
The mare's owner doesn't understand what's going on either,
Nobody knows if the mare is in heat, let alone when she should be served.
just let the veterinary decide! WRONG! And sad, too. Knowing about the construction and function of the equine sexual organs can encourage a positive interaction among the owner, the horse and the veterinary.

Although the following story may be old stuff for one or a bit difficult and dry for another, I would still like to try and present some information about what's going on inside your mare.

The anatomy of the mare
The sexual organs of the mare consist of (from inside to outside):

The ovaries (ovaria)
The fallopian tubes (salpinx)
The womb left uterus
The womb right uterus
The cervix
The vagina
The external opening (vulva)

The ovaries
The ovaries are where the egg cells (ova) develop. When inactive, they are the size of a hazel nut or walnut; when active, ovaries can be the size of a ping pong ball. They are located on the right and left sides in the belly at about the height of the point of the hip, the right one a bit more toward the front than the left. Each mare is born with a certain number of cells in her ovaries that can develop into mature egg cells. An egg cell is microscopic in size and is neither visible on an ultrasound (echo) nor palpable rectally. Egg cells mature inside a fluid-filled sac called a follicle. A mature follicle can reach a diameter of 4 to 5 centimeters, so it is easily seen with ultrasound or felt rectally.

As the maturation process proceeds, the follicle becomes larger and softer. At the moment the egg cell is released from the follicle (ovulation) it floats free in the abdominal cavity for a short time before being picked up by the first funnel-shaped part of the fallopian tube (oviduct). While the follicle develops, it produces hormones: oestrogens (the hormones of oestrus). These oestrogens produce the behaviour typical of a mare in heat.

Once the egg has been released, its follicle develops into the corpus luteum. Although this structure cannot be palpated rectally, it will be visible on an ultrasound. It produces the hormone known as progesterone, the pregnancy hormone that maintains a pregnancy if one develops. When the mare is in foal, the corpus luteum remains intact, if she has not been successfully covered or inseminated, the corpus luteum disintegrates fairly rapidly.

The fallopian tubes
The fallopian tubes guide the fertilized egg cell to the uterus. Fertilization usually takes place in the first section of the fallopian tubes. Unfertilized egg cells come no further than the fallopian tube. The fallopian tubes cannot be felt rectally and arc seldom the reason for infertility in horses.

The uterus
A mare's uterus consists of a fairly small uterine body (corpus) and large left and right uterine horns. The uterus is lined with mucous membrane which, depending on the phase of the mare's cycle, is receiving more or less blood and contains more or less fluid (the best time for breeding being when there is a lot of fluid). This mucus membrane is the site where the embryo will become attached and where a connection (placenta) will develop linking the blood circulation between the mare and her foal. The uterus can easily be palpated and can be seen by ultrasound, but varies in shape and tone (tonus) from mare to mare, e.g.:

a young, 3-year-old mare that has never been covered and is not in heat will have a firm uterus the thickness of a finger, an ultrasound will show no content.
a 16-year-old mare that has had 10 foals and is in 'foal heat' will display a uterus the thickness of a human thigh and will be thick, firm, pasty, and will show content.

The horse has a uterus wit powers of recovery. A horse will into heat again ('foal heat') within 10 days of giving birth. The uterus, too, produces a hormone: prostaglandin F2 alpha. This hormone is produced when the horse is not pregnant and causes the corpus luteum to shrink and disappear.

The cervix
The cervix closes the uterus off from the vagina and is thus the barrier between the sterile (no bacteria) environment of the uterus and the non-sterile environment of the vagina (where certain bacteria survive). The cervix of a horse in heat is loose and relaxed so that instruments, etc., are easy to introduce. The cervix of a horse not in heat is firm and diamond-shaped. When pregnant, the cervix is closed, in the last phase of pregnancy it is plugged shut with a mass of mucous. The cervix is easy to feel and can be seen on an ultrasound display. The cervix can also be viewed by introducing a tube (speculum) into the vagina and shining a light inside.

The vagina
The innermost part of the vagina angles upward to the edge of the pelvis. The urethra empties into the wall near the outermost part of the vagina. At the edge of the pelvis, the vagina starts running more horizontally. In young mares, a hymen is located at this point. No urine or air is found in the vagina of a healthy horse. Although the vagina cannot be felt rectally or seen on an ultrasound display, it can be viewed internally by using a tube (speculum).

Vulva
The external sexual organ of the mare is the vulva. The lips of the vulva should close tightly. Upon pulling them apart, they should slap shut when released.

The oestrus cycle
As everyone knows, the mare goes through oestrus cycles. She usually comes into heat on a regular schedule. A period of heat is when the mare will admit the stallion. This is expressed in both characteristic behaviour and physical characteristics (more about these later). The mating Lime for horses is spring and summer. During this time, a normal mare will come into heat once every three weeks. During the winter, the mare usually goes into an inactive sexual period in which she will not come into heat for several months. In early spring and in the autumn, when the cycles of heat are waxing and waning, the mare can often have irregular periods of heat
Hormones

The reproductive activities of mammals are strongly influenced by hormones. These are substances produced by the sex glands and other hormone-producing glands in the body. The hormones are then transported by the blood and can affect other parts of the body. Their function, thus, is that of a messenger.

The hypophysis, or pituitary gland
Besides the sexual organs themselves, another hormone-producing gland important for reproduction is the hypophysis, or pituitary gland. This is a small gland located in the brain that produces hormones known as FSH and LH (more on this later). A connection between the pituitary gland and the brain exists, so that sensory observations cause by such stimuli as light cause the pituitary gland to produce hormones.

Hormones important for reproduction

FSH: follicle -stimulating hormone. This hormone stimulates the growth and development of a follicle (the fluid-filled sac in which the egg cell develops).
LH. Luteinizing hormone. This hormone stimulates the development of the corpus luteum from the follicle.
Progesterone. This is produced by the corpus luteum and maintains pregnancy.
Oestrogens. These are produced by the follicles and are responsible for the behaviour associated with heat.
Prostaglandin F2 alpha. This is produced by the uterus when pregnancy has not occurred. PGF2 alpha causes the corpus luteum to shrink.

The hormonal regulation of the cycle
There is still a lot we do not know about this subject. Even though it involves a fairly technical explanation, I still want to take a stab at clarifying it by using a set of drawings. Let's begin in the spring. The days are getting longer, it's becoming warmer, and the brain starts sending signals to the pituitary gland to start producing FSH. The ovaries become active and a follicle starts to develop in which an egg cell will mature. The follicle produces oestrogens that result in behaviour typical of heat. When enough oestrogens are produced, the mare comes into heat. Physical signs of this are: swelling of the vulva, mucous production, opening of the cervix, swelling of the uterine mucous membranes. At a hormonal level, oestrogens slow down the production of FSH and stimulate the production of LH. More LH is produced which stimulates ovulation. The egg cell is released and is received by the funnel shaped opening of the fallopian tube (tuba). At this time, fertilization can take place.

After ovulation, the behaviour associated with heat disappears. LH causes the formation of the corpus luteum from what is left of the follicle. The corpus luteum produces progesterone that maintains a pregnancy (if one occurs) and slows down the production of LG. While progesterone is being produced, the horse displays no symptoms of heat.

If no fertilization has occurred (there is thus no embryo in the uterus), the uterus will start producing the PGF2alpha hormone about 14 to 17 days after ovulation. This will make the corpus luteum shrink so that no more progesterone will be produced, the pituitary gland will start producing FSH again, and the entire cycle will be repeated.

In case of pregnancy, the embryo will be recognized by the body and no PGF2alpha will be produced by the uterus. Pregnancy will be maintained by progesterone being produced by the corpus luteum. Later, other mechanisms will also play a role.

Pharmaceutical agents
As you already know, those smart pharmacists have been able to make many hormones synthetically or to isolate them. These can be useful, but arc-, sometimes incorrectly administered to influence the reproduction of a horse. Some of them being used are:

LH/FSH. This hormone is isolated from the urine from pregnant women. (In the Netherlands, this urine is collected under the auspices of a campaign known as 'Mothers for Mothers', although a better name for it might be 'Mothers for Mares'. As part of this campaign, nice little presents are given to donors.)
Progesterone. This is isolated from the blood of pregnant ponies and horses.
Progesterone -like substances (the same ones used in 'the pill'). These are oestrogens and prostaglandins that are made synthetically.

The use of these substances enables us to affect the mare's cycle at practically every level. Often, however, a disturbance in the cycle cannot be attributed to hormonal problems. A familiar example is a horse with a serious uterine infection. This horse can exhibit a defective release of PGF2alpha so that it can either come into heat much too quickly again or may never come into heat again. In this case, the excess or lack of PGF2alpha is not the cause for an irregular cycle; the cause is a uterine infection!



		Introduction Why consulting a veterinary The choice of a stallion The mare The anatomy of the mare hormones The hormonal regulation of the cycle Pharmaceutical agents
	Introduction When it comes to rabbits and humans, it is a known fact that the vast majority of them reproduces without medical intervention. Considering the dramatic increase in the veterinary assistance being given to breeding mares in becoming pregnant, it would almost seem as if no horse could become pregnant without such intervention. Nothing, however, is farther from the truth. Historically, for example, we know that the huge herds of wild mustangs, some of which still populate the American west, descend from only a few animals that escaped from the ones the Spaniards had brought with them to conquer Mexico. Proof, then, that horses don't need veterinary help to reproduce. The reasons why consulting a veterinary is becoming increasingly more common certainly have nothing to do with a charitable attempt to keep me and my fellow veterinaries employed. The real reasons, however, include the following: Semen is expensive. The vast majority of the male horses in Europe has been gelded or is not being used for breeding purposes. The remaining stallions, then, must service many mares. Since a stallion produces, only a certain amount of semen, this is a limited and costly item. The circumstances under which horses are kept are a far cry from the horse's natural habitat. Most mare owners are not at all involved in the emotional or sexual drives of their mares, whilst the conditions under which horses are kept are usually far from natural. Often, a mare is dropped off at the stallion managers location with the only message being, "Good luck", or "Call me when she's in foal". So that's what the stallion manager and his veterinary are faced with -and it's a situation that sometimes has its little surprise-. It can even happen that the mare being brought in to be served can be well along in a pregnancy resulting from being served during the previous season. Costs for keeping horses in general arc high. Since expenses involved in keeping a breeding mare and paying for stud fees are increasing a bit all the time, the pressure 'to perform' is increasing as well. The veterinary is more commonly called in, therefore, 'just to make sure'. In any event, testing for pregnancy has become much more common than it was roughly 10 years ago. A successful conception involves three requirements: A healthy mare A healthy stallion Effective management In other words, a natural cover or insemination requires a sufficiently high amount of semen and must take place at the best possible time. That's about all there is to it. It is sad but true that just as in many human cultures, the failure to become pregnant is usually blamed on the female. Stallion managers too frequently assume that their stallion is blameless and that their management has been impeccable, This means that the veterinary is usually called in to look at the mare. The choice of a stallion is almost never based on his fertility tests. The stallions most in demand for breeding are the ones who perform best in the ring. And when this happens, the availability or the quality of his semen is sometimes not what it should be. The solution might seem obvious: select a stallion that is not so much in demand or is not as old, This choice, however, is up to you. I cannot advise in these matters. Neither can I say much in regard to any problems your own mare might have; you have your own veterinary for this. All the more reason, therefore, for me to discuss the biological functioning of your own mare and that of the stallion you have selected, and what you might be able to do to improve your chances of success, in other words, the management of your one mare or of your entire stud farm. Next, I will address what can and cannot be done in the way of veterinary intervention. After all, we are not miracle -workers. By understanding your own horse better, you can do a great deal to contributing to the success of your breeding program. The mare Breeding mares that are being taken to be served usually undergo routine testing by a veterinary for several reasons. Calling in the veterinary is no longer limited to when a mare fails to become pregnant. This routine testing focuses on determining the right timing for servicing and on checking for pregnancy. Sound reasons for routine testing include the following: The stallion will not have to be used more than is necessary. The amount of semen used (whether shipped or frozen) can be minimized; The number of covers (and thus the mare's risk of infection) will be minimized. Poor reasons: The stallion manager is too busy. The mare's owner doesn't understand what's going on either, Nobody knows if the mare is in heat, let alone when she should be served. just let the veterinary decide! WRONG! And sad, too. Knowing about the construction and function of the equine sexual organs can encourage a positive interaction among the owner, the horse and the veterinary. Although the following story may be old stuff for one or a bit difficult and dry for another, I would still like to try and present some information about what's going on inside your mare. The anatomy of the mare The sexual organs of the mare consist of (from inside to outside): The ovaries (ovaria) The fallopian tubes (salpinx) The womb left uterus The womb right uterus The cervix The vagina The external opening (vulva) The ovaries The ovaries are where the egg cells (ova) develop. When inactive, they are the size of a hazel nut or walnut; when active, ovaries can be the size of a ping pong ball. They are located on the right and left sides in the belly at about the height of the point of the hip, the right one a bit more toward the front than the left. Each mare is born with a certain number of cells in her ovaries that can develop into mature egg cells. An egg cell is microscopic in size and is neither visible on an ultrasound (echo) nor palpable rectally. Egg cells mature inside a fluid-filled sac called a follicle. A mature follicle can reach a diameter of 4 to 5 centimeters, so it is easily seen with ultrasound or felt rectally. As the maturation process proceeds, the follicle becomes larger and softer. At the moment the egg cell is released from the follicle (ovulation) it floats free in the abdominal cavity for a short time before being picked up by the first funnel-shaped part of the fallopian tube (oviduct). While the follicle develops, it produces hormones: oestrogens (the hormones of oestrus). These oestrogens produce the behaviour typical of a mare in heat. Once the egg has been released, its follicle develops into the corpus luteum. Although this structure cannot be palpated rectally, it will be visible on an ultrasound. It produces the hormone known as progesterone, the pregnancy hormone that maintains a pregnancy if one develops. When the mare is in foal, the corpus luteum remains intact, if she has not been successfully covered or inseminated, the corpus luteum disintegrates fairly rapidly. The fallopian tubes The fallopian tubes guide the fertilized egg cell to the uterus. Fertilization usually takes place in the first section of the fallopian tubes. Unfertilized egg cells come no further than the fallopian tube. The fallopian tubes cannot be felt rectally and arc seldom the reason for infertility in horses. The uterus A mare's uterus consists of a fairly small uterine body (corpus) and large left and right uterine horns. The uterus is lined with mucous membrane which, depending on the phase of the mare's cycle, is receiving more or less blood and contains more or less fluid (the best time for breeding being when there is a lot of fluid). This mucus membrane is the site where the embryo will become attached and where a connection (placenta) will develop linking the blood circulation between the mare and her foal. The uterus can easily be palpated and can be seen by ultrasound, but varies in shape and tone (tonus) from mare to mare, e.g.: a young, 3-year-old mare that has never been covered and is not in heat will have a firm uterus the thickness of a finger, an ultrasound will show no content. a 16-year-old mare that has had 10 foals and is in 'foal heat' will display a uterus the thickness of a human thigh and will be thick, firm, pasty, and will show content. The horse has a uterus wit powers of recovery. A horse will into heat again ('foal heat') within 10 days of giving birth. The uterus, too, produces a hormone: prostaglandin F2 alpha. This hormone is produced when the horse is not pregnant and causes the corpus luteum to shrink and disappear. The cervix The cervix closes the uterus off from the vagina and is thus the barrier between the sterile (no bacteria) environment of the uterus and the non-sterile environment of the vagina (where certain bacteria survive). The cervix of a horse in heat is loose and relaxed so that instruments, etc., are easy to introduce. The cervix of a horse not in heat is firm and diamond-shaped. When pregnant, the cervix is closed, in the last phase of pregnancy it is plugged shut with a mass of mucous. The cervix is easy to feel and can be seen on an ultrasound display. The cervix can also be viewed by introducing a tube (speculum) into the vagina and shining a light inside. The vagina The innermost part of the vagina angles upward to the edge of the pelvis. The urethra empties into the wall near the outermost part of the vagina. At the edge of the pelvis, the vagina starts running more horizontally. In young mares, a hymen is located at this point. No urine or air is found in the vagina of a healthy horse. Although the vagina cannot be felt rectally or seen on an ultrasound display, it can be viewed internally by using a tube (speculum). Vulva The external sexual organ of the mare is the vulva. The lips of the vulva should close tightly. Upon pulling them apart, they should slap shut when released. The oestrus cycle As everyone knows, the mare goes through oestrus cycles. She usually comes into heat on a regular schedule. A period of heat is when the mare will admit the stallion. This is expressed in both characteristic behaviour and physical characteristics (more about these later). The mating Lime for horses is spring and summer. During this time, a normal mare will come into heat once every three weeks. During the winter, the mare usually goes into an inactive sexual period in which she will not come into heat for several months. In early spring and in the autumn, when the cycles of heat are waxing and waning, the mare can often have irregular periods of heat Hormones The reproductive activities of mammals are strongly influenced by hormones. These are substances produced by the sex glands and other hormone-producing glands in the body. The hormones are then transported by the blood and can affect other parts of the body. Their function, thus, is that of a messenger. The hypophysis, or pituitary gland Besides the sexual organs themselves, another hormone-producing gland important for reproduction is the hypophysis, or pituitary gland. This is a small gland located in the brain that produces hormones known as FSH and LH (more on this later). A connection between the pituitary gland and the brain exists, so that sensory observations cause by such stimuli as light cause the pituitary gland to produce hormones. Hormones important for reproduction FSH: follicle -stimulating hormone. This hormone stimulates the growth and development of a follicle (the fluid-filled sac in which the egg cell develops). LH. Luteinizing hormone. This hormone stimulates the development of the corpus luteum from the follicle. Progesterone. This is produced by the corpus luteum and maintains pregnancy. Oestrogens. These are produced by the follicles and are responsible for the behaviour associated with heat. Prostaglandin F2 alpha. This is produced by the uterus when pregnancy has not occurred. PGF2 alpha causes the corpus luteum to shrink. The hormonal regulation of the cycle There is still a lot we do not know about this subject. Even though it involves a fairly technical explanation, I still want to take a stab at clarifying it by using a set of drawings. Let's begin in the spring. The days are getting longer, it's becoming warmer, and the brain starts sending signals to the pituitary gland to start producing FSH. The ovaries become active and a follicle starts to develop in which an egg cell will mature. The follicle produces oestrogens that result in behaviour typical of heat. When enough oestrogens are produced, the mare comes into heat. Physical signs of this are: swelling of the vulva, mucous production, opening of the cervix, swelling of the uterine mucous membranes. At a hormonal level, oestrogens slow down the production of FSH and stimulate the production of LH. More LH is produced which stimulates ovulation. The egg cell is released and is received by the funnel shaped opening of the fallopian tube (tuba). At this time, fertilization can take place. After ovulation, the behaviour associated with heat disappears. LH causes the formation of the corpus luteum from what is left of the follicle. The corpus luteum produces progesterone that maintains a pregnancy (if one occurs) and slows down the production of LG. While progesterone is being produced, the horse displays no symptoms of heat. If no fertilization has occurred (there is thus no embryo in the uterus), the uterus will start producing the PGF2alpha hormone about 14 to 17 days after ovulation. This will make the corpus luteum shrink so that no more progesterone will be produced, the pituitary gland will start producing FSH again, and the entire cycle will be repeated. In case of pregnancy, the embryo will be recognized by the body and no PGF2alpha will be produced by the uterus. Pregnancy will be maintained by progesterone being produced by the corpus luteum. Later, other mechanisms will also play a role. Pharmaceutical agents As you already know, those smart pharmacists have been able to make many hormones synthetically or to isolate them. These can be useful, but arc-, sometimes incorrectly administered to influence the reproduction of a horse. Some of them being used are: LH/FSH. This hormone is isolated from the urine from pregnant women. (In the Netherlands, this urine is collected under the auspices of a campaign known as 'Mothers for Mothers', although a better name for it might be 'Mothers for Mares'. As part of this campaign, nice little presents are given to donors.) Progesterone. This is isolated from the blood of pregnant ponies and horses. Progesterone -like substances (the same ones used in 'the pill'). These are oestrogens and prostaglandins that are made synthetically. The use of these substances enables us to affect the mare's cycle at practically every level. Often, however, a disturbance in the cycle cannot be attributed to hormonal problems. A familiar example is a horse with a serious uterine infection. This horse can exhibit a defective release of PGF2alpha so that it can either come into heat much too quickly again or may never come into heat again. In this case, the excess or lack of PGF2alpha is not the cause for an irregular cycle; the cause is a uterine infection! Page up