Weaning can be a very stressful time for the foal. But you can minimize this stress with a little forethought and good management. The trauma of separation is emotional as well physical, and this must be taken into consideration.
The younger the foal, the more stressful the separation, in most cases. A six month old foal is usually more independent and more able to handle the weaning (both physically and emotionally) than a three or four month old foal. Some foals must be weaned early, for various reasons, but whatever the age or reason for weaning, take care to make the transition as smooth as possible for mother and baby.
Horses are herd animals, happiest when with other horses. One of the most traumatic ways to wean a foal is to separate him completely from his dam and leave him alone. It's better to put the foal where he can at least see and hear other horses and not feel isolated. Avoid total separation if at all possible. Left alone in a box stall or small corral, the foal may literally try to climb the walls. The traditional way of weaning (mare and foal completely out of sight and sound of one another) is probably the most stressful way to wean.
Some people wean their youngsters as a group, penning them together. Unfortunately, the insecurity of these youngsters can be contagious. More often than not, a group of weanlings will pace the fence, calling for their mothers, running and stirring up dust. The dust raised can irritate young lungs and cause Pneumonia, especially in the stressed animal. Frantic activity by one foal usually sets off all the others, thus they rarely have a chance to rest or stop their worrying long enough to eat.
In the wild, young horses are still part of the herd when weaned, and have adult horses for protection and security. Our domestic well-fed foals really don't need their mothers' milk after about six months of age and are physically ready to be weaned. But they are not emotionally ready for total separation from mother or the herd. It is much easier on a foal if weaning can take place in such a way that he can still be near his dam, at least initially.
The least traumatic way to wean a foal is to put mother and foal into separate adjoining pens for a few days, if the pens are constructed in such a way that the foal cannot reach through the fence to try to nurse and with the partitions high enough that neither the mother nor foal will try to jump over. The foal can still see and smell his mother and will benefit from the emotional security of having her close.
Foals weaned in pens adjacent to their dams usually spend most of their time near the fence that separates them, but they aren't as worried as other weanlings. There's much less whinnying and fence pacing. They may sniff and nuzzle each other through the fence, but the foal cannot nurse. After a few days the foals can then be totally separated from the mares without ill effects, especially if they have other horses for company. Once the mares have started to dry up their milk flow, they will no longer be so urgently interested in having baby by their side.
We started weaning our foals this way (with mare and foal in adjoining pens) eight years ago and it has worked much better the method of total separation. Most foals manage the transition very smoothly within just a few days. One very independent young filly was so at ease with this type of separation that we left her and her dam in adjoining pens for only one day before putting the filly in her old pasture with a yearling for a buddy, with no problems.
Colts often seem a little more insecure than fillies, and some of them take a little longer to let go of the apron strings. One little "mama's boy" needed the security of mother through the fence for more than a week before we felt he was ready for the final transition. When we took mom to another pasture after that, he paced the fence a while and yelled his displeasure, but he was basically weaned, and much less frantic than he would have been if he'd been totally separated at the beginning.
Anything you can do to minimize stress at weaning time is very important. Too much stress can lead to sickness, because the foal's immune defenses are lowered if he is emotionally upset and not eating properly. Stress may also lead to injury if the foal spends a lot of time running frantically or trying to get through a fence. The worried foal may spend a lot of time running, working up a sweat, and then chill (especially if nights are cold, as they can sometimes be in the fall at weaning time). Bad weather at this stressful time can lead to sickness in stressed foals.
Pens and pastures used for weaning should be absolutely safe, without hazardous obstacles, loose fencing or poles, and so on that a foal might run into during his efforts to get out. If several foals are to be put into a weaning pen together, the pen should be large enough to give the more timid foals a chance to get out of the way of the aggressive ones. The emotional trauma of weaning usually makes the aggressive foals even more aggressivethey take out their frustrations on the underdogs. But the pen should not be so large that a foal could get up a lot of speed in frantic running. If allowed too much room, a truly frantic foal may try to jump a fence or crash into a fence because he's running too fast to stop and turn in time.
This type of behavior is rarely a problem if foals are weaned in a pen next to their mothers, but make sure the partition between mares and foals is adequate to prevent any attempts to reach through and nurse. I prefer small-mesh wire, if the mesh is small enough the foal can't put a foot through. (Diamond-mesh works very well for this.) If a portion of the fence, such as a gate, has spaces large enough for a foal to put its head through, cover that space with plywood, mesh wire, or a safe type of covering that will prevent any reaching through.
Your foal will also fare better if he is accustomed to the feed he'll be getting. If he's been on pasture with his mother, bring the pair in for a few days before weaning and begin feeding hay. If the foal starts eating hay and grain while still on his mother (using her as an example to follow) he'll be better prepared. A foal that has not had grain before may not be interested in it at all when he is emotionally upset. But if the foal has learned to like hay or grain from p;revious experience, he'll be more likely to eat it during weaning.
Avoid any new stresses when weaning. Schdule activities such as de-worming, vaccinating or halter breaking a foal. before the weaning, or wait until the foal is well started in his new lifestyle. It's usually much easier on the foal if some of the training and handling is already behind him. If the foal is already used to human handling and companionship, he'll tend to look to his human handlers for comfort and food when mama is no longer there. This can make the transition much easier for both the foal and his caretakers.
Don't put your foal into strange surroundings to wean him. He'll find comfort in familiar surroundings. We like to put the mare and foal into the weaning pen for a few days ahead of time, then move mama into the adjacent pen, leaving the foal in the familiar pen.
Some mares are just as emotionally upset at weaning time as their foals are, so the mare's enclosure should be just as safe as the foal's. With careful planning, you can make weaning a less stressful time for your mare, your foal, and yourself.