A hay-only or even a grass-only diet may indeed provide enough calories to keep weight on any horse, if the hay and/or grazing are in sufficient volume. However, what may be lacking are the necessary vitamins and minerals, and even more importantly a balance of the correct vitamins and minerals. Without a hay and/or pasture analysis, achieving a correct balance may be impossible, so it then becomes necessary to try to cover your bases. An all-forage diet is perfectly fine if the mare can maintain her condition with that; however, in order for her to receive maximum nutrition, at the very least a mineral supplement should be provided with special attention to selenium levels/vitamin E if you live in a selenium deficient state. Calcium
hosphorus ratios are also a concern with the all forage diet, particularly in a pregnant mare.
Horses in the western part of the US are commonly fed an all-alfalfa diet, so that in itself may not be a problem. Minis tend to obesity, however, and the all-alfalfa diet may provide too many calories (and calcium) if not fed correctly. All horses should receive a minimum of 1% of their ideal body weight in long-stem forage (hay or grazing) per day for proper gut health, so hay should be weighed rather than measured in "flakes" or "half flakes". The rule of thumb for pregnant mares is to feed maintenance quantities until the latter part of the term when the in utero foals are building their own weight, thus drawing more from the mare. The term "maintenance", however, may vary by individuals and would depend on the mare's metabolism. Some easy keeping mares might require only 1% of body weight, while others might require the more average amounts of 1.5-2% of body weight, while some might require as much as 3% of their body weight in feedstuff per day to maintain body condition. An overly fat broodmare is not necessarily a healthier broodmare, though most breeders tend to like their mares "fluffy", especially towards the end of term in preparation for the caloric demands of nursing.
An average sized miniature mare weighing in the 200-250 lb range would require a minimum of 2 lbs of hay per day (1% of body weight), and maybe as much as 6+ lbs (3% of body weight) on the high end. This would need to be balanced, at the bare minimum, with a legume (alfalfa) balancer mineral which contained more phosphorus than calcium. There are several good products on the market which would fulfill this need.
Robin C
