Imprinting: The Great Debate

In a rundown of this early foal handling technique we explore its benefits and drawbacks

Horse ownership and parenting share a number of parallels. Everyone is happy for you, and everyone has advice. Articles, research, and anecdotes abound, and often they all seem to contradict. At no point does owning a horse feel more like parenting a child than after the birth of a foal.

Fortunately, owners of a new foal rarely have to consider nursing vs. formula, and the diaper debate is moot. However, when it comes to education (training), horse owners face as many conflicting viewpoints as new parents. Questions arise around the handling of the new foal: How much? How soon? Will handling the foal disrupt the bond with the mare or delay nursing? Will it make for a more tractable foal? What about imprint training?

The First Few Hours: Foal Brain and Needs

In The Lion King the hyenas gnaw happily on the haunch of a zebra. Zebras, antelope, cattle, and, yes, horses are prey animals. Their place in the circle of life is just above the grass. But unlike horned antelope and cattle, horses don't have much in the way of weapons. While the impact of a well-placed hoof can be significant, those hooves are better designed for gaining traction in flight than they are for fighting.

Prey animals that give birth in the open (such as horses and cattle) generally produce what are known as precocial young--offspring capable of using all of their senses, standing, nursing, and moving rapidly out of danger's way within hours of birth. In contrast, predators and animals that give birth in safe burrows typically bear altricial young. Altricial neonates (newborns) have limited sensory capability (eyes and ears are closed or minimally functional at birth); possess limited ability to regulate their own body temperatures; and generally lack the ability to support their bodies, move in a coordinated manner, or seek food themselves. While most altricial (dogs, cats, humans) neonates get most of their maternal immunity through the placenta, precocial species generally must ingest the bulk of their maternal antibodies from their mothers' colostrum, or first milk.

These species develop different bonding patterns based on their needs for safety, shelter, and nutrition. For survival, mother-offspring bonding is less critical for altricial species than precocial. Pups' ability or inclination to follow their mother is irrelevant shortly after birth, but it is essential that she stay with them, feed them, and not maul them. For precocial species, however, it is critical that the neonate learn to recognize, bond with, and follow mother.

Researchers first documented the behavioral phenomenon called imprinting in the 1800s, but Austrian Nobel prize winner Konrad Lorenz, MD, PhD, made it famous in the 1930s. While studying geese, Lorenz noted the immediate attachment of the young to the mother--the first moving object that the goslings saw. He then discovered that by making himself the first moving thing that the young birds saw, they would attach (imprint) onto him, ignoring their biological mother.

"Imprint Training"

The foal handling technique dubbed imprint training by Robert M. Miller, DVM, a California equine veterinarian, relies upon the precocial neonate's sensory awareness and is based on desensitizing the foal to unpleasant (noxious) stimuli.

According to Miller, imprint training has a threefold purpose:

To create a "bond between the subject (foal) and the human. The foal memorizes the odor, sound, and appearance of the first moving thing it sees," says Miller.
To "desensitize the foal to normally frightening stimuli. This can be done at any age," says Miller, "but right after birth is most convenient."
To teach the foal to "respect humans as leaders; to teach to yield head, neck, and feet."
However, according to Katherine Houpt, VMD, PhD, Dipl. ACVB, professor emeritus at Cornell University, Miller's technique is not "imprinting" in the behavioral sense. Houpt instead calls the technique "desensitization to touch." For this, she says, "there doesn't seem to be a particularly sensitive period (hence, the foal should learn at any point). However, a lot (regarding the success of any handling technique) has to do with what happens subsequently."

For example, a foal that becomes ill or injured and is receiving injections daily might perceive handling as noxious regardless of early conditioning.

Miller agrees that this technique is not technically imprinting. He uses the term imprint training to refer to the process of "habituation during the imprinting period." He believes this early period is primed for peak learning in the foal.

Briefly, Miller's technique involves handling the neonatal foal in a recumbent (lying down) position--ideally before it first stands. While the foal is still down, Miller stimulates each part of the foal's body repeatedly until the foal appears to accept the stimulus: He rubs the foal all over his body, raps the bottoms of his feet, inserts a finger into all body openings, and touches the foal with both plastic and paper, repeating each stimulus 100 times. He says 30-50 repetitions of a stimulus generally are required to habituate the foal to that stimulus; the first session lasts anywhere from 30 minutes to 2 ½ hours, with the average session lasting an hour.

Miller says he prefers to begin the neonatal session as the mare delivers the foal, while both mare and foal are still lying down. If the foal has already stood, he likes to have the mare haltered and held and to lay the foal back down for the session. He suggests allowing the mare to lick and smell the foal while the handler works.

At the second imprinting session, usually the day after foaling, "providing that the foal is agile and normal on its feet," Miller says he repeats the stimuli of the previous session and begins halter training, asking the foal to lead, back, turn left and right, and turn on both the hind and the forelimbs. Miller stresses the importance of conducting not only this second session but also multiple follow-up sessions.

On this note he says the two most common "mistakes" he sees people make with the imprint training method are:

Rushing the birth session. Miller believes if the handler performs an inadequate number of repetitions for each stimulus, the foal is "sensitized" and provoked to a flight response from that stimulus, but the process fails to "proceed to habituation."
Not completing subsequent training. The foal shows discomfort with handling, so the handler stops the sessions. In Miller's opinion, failing to provide subsequent sessions creates a "horse that is unafraid but with no respect for humans."
Limitations and Concerns

Just as other precocial young, a foal obtains the majority of his antibodies through his dam's colostrum. Antibodies are large molecules that would not normally be able to cross the intestinal lining and enter the bloodstream. However, for the first several hours after birth, the foal's gut wall is "open," or permeable to larger molecules. Within 12-24 hours after birth, this permeability "closes," and colostral antibodies are no longer able to enter the blood. Therefore, the foal must drink adequate amounts of colostrum in the first hours after birth.

Houpt says that while several studies have shown imprint training's later effects on immune status to be minimal, the only real harm of using the technique "would be if you perform (the first session) for so long that the foal is in danger of gut closure" before he consumes the crucial colostrum.

While Miller does not recommend a session lasting more than two to three hours, it is important to remember there is often a delay of an hour or more between the time the foal stands and active nursing. Miller does recommend milking the mare and having a second handler bottle feed 4-6 oz. of colostrum to the foal during the first desensitization session.

Many owners and behaviorists have raised concern with the risk of disrupting the mare-foal bond with imprint training. Miller asserts that when done properly, his technique results in a "three-way bond between mare, foal, and handler."

In a study performed in France1 researchers examined foals separated from their dams and handled for one hour after birth within visual range. They compared their later behavior to a control group left undisturbed with their dams following birth. They found that the experimental (handled) foals "presented patterns of insecure attachment to their mothers ... at all ages." However, though the researchers in this study used Miller's techniques, the physical separation of foals and dams and lack of follow-up sessions make it difficult to draw comparisons. As for imprinting and foal acceptance by dams, in a study Houpt performed involving Arabian horses, foal handling did not appear to be a factor in foal rejection. Houpt acknowledges that "if a mare is human-oriented, the mare may be more attracted to the foal if it is being handled."

Handling stress and its impact on the foal's well-being is another point for examination. In the 2008 paper2 "A review of the human-horse relationship," the authors note that "in natural herd conditions mares actively seek isolation two to 24 hours prior to foaling." They also state that "the rupture of the dam-foal bond, even on a short-term basis, induces extreme distress." This same review of the literature commented in regard to imprint training "that the foals show a high resistance to the procedure and show signs of stress."

Says Miller, "I agree. If you take a horse of any age and start working with it, will it show resistance? You bet. Everything new is stressful to a horse. Horses respond with the desire for flight to any novel stimulus at any stage of its life."

But Does It Work?

Miller reports success using his technique both for short-term and long-term handling and manageability. His anecdotes of positive results include the following:

A group of Thoroughbreds in Poland were trained based on techniques Miller taught at the same facility in 2009. On a subsequent visit in 2010, weanlings were brought before Miller and presented with a number of stimuli including dragging plastic sheets and tin can rattling. The weanlings stood calmly.
A ranch owner has a herd of 30 imprint-trained zebras that are reportedly "gentle enough for children" to handle.
A number of Miller's own and client-owned horses over a 50-year span have displayed positive manners, a bond with humans, and human respect. "In 50 years I've never had a failure," he says.
Other trainers in the natural horsemanship movement who have expanded upon these techniques include a trick horse trainer in Texas who has "gone further with this training than anyone I know," says Miller.
However, results from controlled trials are somewhat limited. The earlier-cited review of literature on the human-horse relationship references studies that showed "no beneficial effects on foals' behavior when tested at 1, 2, and 3 months of age or at 6 months of age." However, other studies have shown short-term positive effects including the foal approaching the handler more easily and tolerating hind feet handling. There has been variability in the methods used in studies examining neonate handling, so the questions of method influence and handler experience are still unresolved.

It is of interest that in one study brushing foals gently for 15 minutes per day was a positive predictor of future foal behavior, having as much effect or more than simple day-to-day handling of the foal.

Take-Home Message

Regardless of whether you intend to pursue imprint training, positive interactions with a calm, trained mare and repeated positive, and consistent interactions with the foal seem to be key factors for successful handling. And, as with any equine training method, attention to human and horse safety and the presence of experienced personnel are critical.

References:
1. Henry S, Richard-Yris M-A, Tordjman S, Hausberger M (2009) Neonatal Handling Affects Durably Bonding and Social Development. PLoS ONE 4(4): e5216. doi: 10.1371/journal.pone.0005216
2. Hausberger M, Roche H, Henry S, and Visser E.K. "A review of the human-horse relationship." Applied Animal Behavior Science 109, 1-24. 2008