South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
and possibly laminitic horse. In the absence of forage analysis, hay can also be soaked for 30-60
minutes prior to feeding in an effort to leech out some of the soluble carbohydrate.
Dietary management of overweight horses: It is clearly difficult to have owners comply with
dietary recommendations that eliminate all concentrate feeds and pasture turn out for their
overweight horses. Thus, I recommend that a horse owner approach the problem of an obese
horse in much the same way that they may have to approach a family member with a substance
abuse problem. An intervention is needed and for the horse the drug is too much feed. If an owner
accepts this approach and follows strict dietary recommendations for 60-90 days, improvement
(specifically weight loss) can usually be seen providing positive reinforcement for further owner
compliance.
It is commonly assumed that an adult horse requires 2% of its body mass in daily forage intake for
maintenance. However, horses with EMS are “easy keepers”, likely due to presence of thrifty
genes and they may need only 1.5% of their body mass in daily forage. In the 6th revision of the
Nutrient Requirements of Horses (2007) prepared by the Committee on Nutrient Requirements
for Horses of the National Research Council Board on Agriculture and Natural Resources, the
average recommended daily energy intake for a sedentary adult horse (1000 pounds) was 16.7
Mcal/day with a minimum value of 15.2 Mcal/day. The latter amount digestible energy can easily
be provided by 15 pounds of good quality hay daily. To put energy intake into perspective, if an
owner feels they must add a pound of concentrate feed twice daily to the ration, this would
increase daily energy intake by 3 Mcal/day (to about 18 Mcal/day). After a year, an additional
1000 Mcal would have been fed and would have produced a 100 pound increase in body mass!
Thus, in order to produce weight loss, even less than 15 pounds of hay needs to be fed daily.
However, this feed restriction can lead to an unhappy horse that may start chewing on wood or
other parts of its surroundings. A compromise can be achieved by finding a lower quality of hay
(generally a mature grass hay) that could be fed in a similar amount. If an adequate hay source
cannot be identified, soaking the hay would be another option to decrease energy content. The diet
is started at 1.5% of the horse‟s body mass but it is important to realize that current body weight
is greater than ideal body weight. As a consequence, forage intake is slowly decreased over 2-4
weeks to 1.5% of the target body weight. The only way that such a diet can be appropriately fed is
to weigh the daily hay ration. This can easily be accomplished by placing the daily ration in a hay
net or plastic bag and holding it while the owner steps on their bathroom scale (that they have
brought to the barn).
A weight loss of at least 50 pounds is required to produce a numerical reduction in body condition
score. This can be loosely equated to an energy deficit of about 350 Mcal for the average adult
horse. The goal should be to accomplish this 50 pound weight loss within 60-90 days after the
diet has been started. If that target is not reached, a further reduction (10-15%) in hay intake will
be required or hay soaking will need to be started if not yet implemented. Once ideal body weight
has been achieved, it is clearly important to continue to limit feed intake and provide minimal
pasture access in order to maintain ideal weight.
Further management of overweight horses: Another important management tool is
implementation of an exercise program. A caloric deficit can be accomplished both by limiting
feed intake as well as by increasing caloric expenditure through exercise. It is well recognized that
overweight human patients accomplish and maintain weight loss more effectively if diet is
combined with an exercise program and the same is likely true for horses. Unfortunately, the
major complication of EMS is chronic laminitis and a painful gait may limit the ability to
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