Question

Serena is my seven-year-old, HYPP-positive Quarter Horse mare that weighs about 1,200 lb (550 kg). She is in light rehab work six days a week, more walking than trotting. She is kept outside at all times in a drylot, and she is fed 16 lb (7.25 kg) of fescue hay each day. She is also given 1 lb of balancer pellets and 2 lb of oats per day. Will she maintain her current weight on this diet or should I add a bit of high-fiber, high-fat feed?

Answer

There is a difference in digestible energy (DE) between oats and the high-fiber, high-fat feed, but it is not extreme. The biggest difference in the two is where the energy is coming from: oats has starch energy, whereas the other feed has energy primarily from fiber and fat, as the description suggests.
Here’s a quick comparison of the DE:

DE content of oats = 3.28 Mcal/kg
DE content of the high-fiber, high-fat feed = 3.43 Mcal/kg

If you’re trying to maintain her weight, it may be sufficient to feed this little bit (1 lb) of the high-fiber, high-fat feed in addition to the oats. Because this is still far below the recommended feeding rate of the high-fiber, high-fat feed, it would be important to feed the balancer pellet, but you could cut the amount down to half a pound.

If you decide to feed more of the high-fiber, high-fat feed, then there might be a further complication with your HYPP-positive mare because of the potassium content. There is a difference in the amount of potassium in the high-fiber, high-fat feed and in oats, even though most of the potassium is coming from the forage.

Comparison of potassium in the two feeds:

Potassium contents of oats = 0.45%
Potassium content of the high-fiber, high-fat feed = 0.9%

Therefore, a possible diet for this horse could be 1/2 lb oats, 1 lb high-fiber, high-fat feed, and 0.25 lb balancer pellet per feeding, fed two times per day.