Weaning is less stressful on foals if they are given the company of familiar adult female horses, even if they are not related to them, Austrian researchers have found.
Professor Christine Aurich and her team at the University of Veterinary Medicine, in Vienna, found that how weaning takes place in a foal can have a dramatic effect on the time required to overcome the shock.
The study has just been published in the current issue of the journal, “Stress”.
In the wild, horses are usually weaned after about a year, typically until their mothers are next about to give birth.
Weaning takes place gradually – the mothers discourage their young from suckling and do not produce as much milk – and so the foals gradually come to rely on other sources of food.
Contrast this with the situation for domesticated foals, which are generally removed from their mothers abruptly and at a much earlier age.
The young animals are suddenly deprived of their main source of nourishment as well as the emotional security that their mothers provide.
For the mares, without her foal to care for, this also represents a significant change in lifestyle.
Aurich and her colleagues compared the levels of stress suffered by foals when weaned by different methods.
Regina Erber, a member of Aurich’s group, examined three ways in which female foals can be separated from their mothers.
One group of foals (A) was subjected to the “short, sharp shock” method – the mothers were all removed from the foals’ stable at once.
Another group (B) was treated in the same manner, but two other mares, not related to any of the foals, were present from the foals’ birth until the end of the experiment.
The final six foals (group C) were subjected to sequential removal of the six mothers, with two mothers taken away each day for three days.
The animals’ behaviour under each scenario was closely monitored to see how they adapted to independent life.
Levels of stress hormones in the foals’ saliva were measured and their heart rates were followed (changes in heart beat are associated with stress).
The results were dramatic, the researchers found.
It was clear, they said, that weaning under any circumstances was extremely stressful.
All foals lost weight after being separated from their mothers and the levels of stress hormones in their saliva were similar to those found when horses are transported, which is known to be associated with a high degree of stress.
The hormone level immediately after weaning was not found to depend on the method of weaning, so it seems that irrespective of the weaning procedure the animals are discomfited.
But there were significant differences in how long it took the foals to come to terms with life without their mothers.
The researchers found that foals in groups A and C needed much longer to gain weight after weaning than foals in group B, and showed many other classical signs of stress. For example, they whinnied more often and spent more time walking around, presumably searching for their mothers.
It was clear, the researchers said, that weaning foals in the presence of other mares helped reduce the length of time they suffered.
Aurich interpreted the results in relation to the situation in wild horses.
“We know that horses in the wild usually live in family groups, with one mature stallion and several mares with their offspring.
“Having other mares present when foals are weaned is thus closer to the natural situation and seems to help compensate for the removal of the foals’ mothers.”
The presence of a “support group” seems to help foals accept the loss of their mothers.
The researchers noted they had yet to consider how the mothers may be helped to come to terms with no longer having their foals around them.
Vienna’s University of Veterinary Medicine is the only academic and research institution in Austria that focuses on veterinary sciences.