Inducing lactation in surrogates
"Now that we can produce maternal behavior, I would advise a large breeding farm to have a mare that they can induce lactation
in and then can stimulate maternal behavior when they need it, rather than having to purchase an expensive nurse mare, whose
own foal then is an orphan," says Houpt.
The first step is to bring the subject mare into lactation. "You give them estrogen and progesterone, followed by sulpiride,
which is a tranquilizer, but it also stimulates the release of prolactin from the pituitary, which will stimulate the mammary
gland to produce milk," says Houpt. Domperidone can also be used in lieu of sulpiride.
"Inducing lactation in a surrogate mare works especially well with mares that have previously successfully raised a foal,"
says Houpt. "It has not worked with mares that reject a foal. It works best with those mares that you know are good mothers,
even ones that are aggressive to other adult mares. Inducing lactation is best used with a mare that is multiparous but just
happens to be available as a surrogate mother because she is barren."
Once lactation is produced, it helps to stimulate her to accept the foal and allow it to nurse. "To do that, you stimulate
the cervix, via the vagina, twice for two minutes at 10-minute intervals," Houpt says. "The mare should then accept the foal
because what you're doing by cervical stimulation is mimicking vaginal delivery."
The cervical stimulation causes the nerves in the brain to promote oxytocin release into the blood stream to produce milk
let-down and at the same time into the olfactory bulb of the brain, thereby allowing the mare to recognize the foal by smell.
"This then creates the maternal trigger for the mare to recognize the foal," says Houpt.
A recent article notes stimulation of maternal behavior without vaginal stimulation using a similar protocol except with a
single injection of a large dose of prostaglandin F2-alpha, which is presumed to release oxytocin in the brain.1
According the article, "barren mares that have raised several foals tend to have a mammary gland that is more developed and
a more predictable maternal behavior."1 Since these mares are not pregnant, they must be given a very sufficient energy-rich ration because they do not have the
same propensity to ingest large amounts of food. The study suggests that the mare be given estradiol benzoate (50 mg/500 kg)
and altrenogest (22 mg/day orally) and twice-a-day injections of sulpiride (1 mg/ kg intramuscularly every 12 hours).1 Once the mammary gland has increased in size and filled and milk drops are present, the mare should be milked five to seven
times a day for three to seven days. At three to four days with the mare producing about 3 to 5 liters per day, she is ready
Using a modified method, another author induced lactation in nonpregnant mares by administering 150 mg progesterone and 50
mg estradiol-17-beta (once daily for seven days on days 1 to 7 ), followed by 5 mg prostaglandin F2-alpha given intramuscularly
on day 7 along with 500 mg sulpiride given twice daily on days 1 to 10.2 A foal was placed with each mare beginning on day 1. Oxytocin was administered at 5 IU occasionally. Using this protocol,
about 80 percent of treated mares lactated.
Reestablishing the bond
If not creating a surrogate, but trying to correct aberrant behavior in more difficult mares, Houpt recommends putting them
behind a pole so that they can't move sideways and tying them so that they can't bite the foal. "Also make sure the foal can't
get in front or behind the mare or underneath her so that she can't hurt it," says Houpt. "With the mare so restrained, the
foal should be able to get to the udder whenever it likes to easily nurse without a concern of injury."
The reason it is so important to coerce the mare to accept it is that the foal normally suckles every 15 minutes. If the foal
has its own access as opposed to your trying to periodically bring the foal to the mare, you are much more likely to get acceptance.
You are also much more likely to get acceptance if the foal is within eyesight of the mare and can suckle frequently.
If the mare just doesn't want anything to do with the foal, rejects it or doesn't allow it to nurse, it may think it is another
mare's, says Wolfsdorf. "Farm managers are very good about working with these mares, either rubbing the placenta or the mare's
manure on the foal to give the foal the mare's smell so the mare then realizes that the foal is hers," she says. "Once the
foal makes 'milk-poop' it will also help to promote recognition that the foal smells like her, so she will accept it as her
own." Sometimes the unintended consequence of haltering young foals is that the halter might smell of previous foals that
have worn them. "This might cause the mare to reject the foal as not hers," says Wolfsdorf.