In the world of horse breeding, the production of strong, healthy foals with desirable temperaments and functional conformation, is the primary goal for horse breeders. Breeders and mare owners work hard to achieve a pregnancy, to obtain a live healthy foal and to produce an unblemished horse with a good attitude and which sells for a profitable sum.
Breeders must produce such foals yearly to maintain their business. So a weaning period determined by the breeder, is an integral part of the breeding industry.
Why weaning is stressful
Before weaning, foals receive both nourishment and a sense of security from their dams. The milk provides vital nutrients for the survival, health and growth of the foal, while the dam herself provides safety and comfort. Foals will usually nurse not only for sustenance, but also after they have been briefly separated from their dam, or frightened. Thus weaning is one of the most stressful periods in a foal's life.
Most breeders agree that the weaning process is stressful, based on behavioural display of the foal and its mother. Research projects – involving the measuring of heart rate, walking, vocalisation and cortisol response in foals at the time of weaning – confirm this. The addition of risks to the immune system as well as risks of injury for both mare and foal are factors breeders consider when weaning.
Chronic stress has been found to cause chronic gluccocorticoid secretion which can put pressure on the immune system, cause gastric ulceration and which can stunt growth and reproductive function.
What is stress?
Stress, in the case of weaning, is defined by researchers as "any situation that requires the foal to make abnormal or extreme adjustments in its physiology or behaviour in order to cope with the adverse changes in its environment or management".
In studies conducted during weaning, certain typical physiological responses to stress or anxiety were observed. In the presence of stressors, the brain responds by releasing adrenocorticotropic hormone (ACTH) from the anterior pituitary gland. ACTH then stimulates the adrenal glands to secrete cortisol.
Cortisol acts on several organs, especially the liver and kidneys, to alter their metabolism. Although cortisol is important in coping with short-term responses to anxiety, long-term cortisol production can lead to illness and suppressed immune responses by the body.
There are two methods commonly used in studies on measuring stress or anxiety in animals. The first is the measurement of blood cortisol concentrations, and the second is analysis of the sensitivity of the adrenal gland to ACTH during and after a stressful event. Elevated blood cortisol levels indicate stress, while lowered cortisol output in response to ACTH release indicates that adrenal cortisol has been depleted by long-term stress. Therefore, ACTH-stimulated cortisol release is used by researchers to measure adrenal competency, thereby determining the degree to which the animal was stressed.
Weaning methods
Many different weaning systems have been devised by breeders over the years, with the choice of system depending on facilities, numbers of foals, experiences and preferences of breeders. Some wean foals in stables, while others wean them in small pens or large paddocks. Foal weaning age and methods of weaning have also varied.
Traditionally, foals were weaned abruptly, at once. They were often weaned in pairs or groups as this was thought to ease the stress of separation from the dam. However, studies have shown that the exposure to new surroundings, a new herd or companion and separation from the dam all at once actually pose a more stressful situation for the foal.
Research experiments concluded that partial, gradual weaning techniques – where foals are separated from mares by safe paddock fencing so that they cannot suckle but can see, hear and touch their dams – are far less stressful to foals. Mares also experience less stress in this way. This is beneficial for their immune and reproductive systems.
This method essentially involves creep feeding of hard feed (concentrates and cut grass fed to foals via special lowered creep feeders at the time when mares are fed their meal from higher troughs) which is vital in this weaning process and for the foals' adaptation to hard feed. Foals need to be consuming adequate creep feed prior to weaning to ensure that their digestive systems have adapted to the feed and to prevent digestion problems that occur when hungry foals, consuming too much feed, overload their gut.
Vaccinations, deworming and castration should ideally be done far in advance of weaning or at least one month after foals have been weaned. In the past, this was often done simultaneously with weaning, but this only adds to the stress levels for the foal.
What age to wean
The age at which foals are weaned varies between breeders from neonatal (post-birth, due usually to rejection of the foal by the dam, death of the dam or shipping home from the breeder) to 4-6 month, or 7-8 month or "natural" weaning.
It has been found in studies that the age at which a foal is weaned, may affect its ultimate position in the herd hierarchy, as it matures. Early weaning may have been advisable for owners of mares with undesirable dispositions, since temperament and aggression may be learned behaviour. Late weaning may increase chances of transferrance of good dispositions from such mares, although this can put unnecessary demands on the mare's energy stores, leading to loss of condition.
By the age of four months, the mare's milk no longer provides adequate energy requirements (although still meeting mineral requirements) for the foal and it will seek out hard food. Today, many breeders wean foals at 4-6 months of age.
Handling foals during weaning
Researchers conducting experiments on the handling of foals at various ages discovered that, while imprint handling post-birth and the handling of foals prior- or post-weaning did not have a significant long-term effect on foals, handling of foals during the (partial, gradual) weaning process had positive long-term results in terms of lasting manageability of those horses as they matured.
It was found that the combination of low-level cortisol output from the low-level stress of gradual partial weaning – and removal of the foal from the comfort zone of its dam – allowed not only for easier handling as a result of the foal seeking company and reassurance, but also for retained learning and acceptance of human handling.
Thus weaning, using the partial, gradual method, is an optimal time to introduce handling such as haltering, leading and picking up of feet. Foals handled at this time also responded better to new environments, short-term isolation tests and surprise tests including intimidating objects. These foals developed into more confident, relaxed, manageable horses.
A well-handled, secure foal develops into the manageable, well-rounded horse that the breeder can sell with confidence.
(References available from the author)
