This section is from the book "The Horse - Its Treatment In Health And Disease", by J. Wortley Axe. Also available from Amazon: The Horse. Its Treatment In Health And Disease.
The longer a foal can have the easily assimilable milk of its dam the better horse it will make. But for various reasons mares are but seldom permitted to wean their own foals, partly because they are required to take part in the work of the farm or to be used for riding or driving purposes, and partly also because they have again been put to the horse and are building up another foetus. Although these several duties are capable of being performed within certain limits without ill effects either to parent or progeny, when pushed too far they are likely to prejudice the health of both. As the foetus of the pregnant mare increases in size and attains to higher development, suckling can only be carried on at a disadvantage to the former, and a heavy drain on the nutritive resources of the latter.
Foals are usually weaned about September or October, when they are five or six months old. At this period of the year, nights are getting cold and damp, pastures are on the wane, the milk-supply is falling away, and if the mare has been to service her foetus has made considerable growth and requires all her support.
Where, as the result of constitutional weakness or debility, from backward growth or any other cause, it is considered desirable that the foal should continue with the dam for an extended period, then both should be allowed an ample supply of corn and chaff, and any demand that is being made on the mare in regard to work should cease.
Animals when called upon to extend the period of suckling, should be taken up early and put into a well-littered yard, and have the protection of an open shed.
In all cases the foal should be well "done" with corn, bran, and chaff for three or four weeks before being weaned, so that the loss of the mother's milk may not be so severely felt.
As to whether the separation of the foal should be made completely at once, or by allowing it to return to the mare at increasing intervals, is a matter upon which breeders are not by any means unanimous, some adopting the one course and some the other, with equal success and satisfaction. We think, however, that a gradual intermittent process of weaning is most rational, and best adapted to safeguard the health of both dam and offspring.
For some time after separation takes place the mammary gland of the dam continues its secreting function, and in the case of mares in whom lactation is very active may cause painful distension of the udder. To avoid this, the quantity and milk-forming quality of the food supplied to the dam should be reduced, and only a moderate measure of water allowed.
After weaning, foals should not be allowed to "go back" in condition, but should be kept growing by a liberal ration of manger food and good pasture.
The restlessness resulting from separation from the dam will be greatly appeased by company, and especially by two or more foals being turned out together.
 
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