Rich bran is the middle layer of the rice kernel.  The outer layer is the husk that is removed to make brown rice.  The middle layer is the bran that, when removed, leaves white rice and bran.  It is this brown layer of bran that is feed to horses (and humans too).
The bran layer makes up less than 10% of the total weight of rice but contains 60% of the kernel's nutrients (a good reason for you to eat brown instead of white rice). This is why the bran, instead of just rice, is a good supplement for horses. 
For horses, bran supplementation can provide a number of benefits including:
  1. Providing necessary energy to high activity horse
  2. Providing healthy calories to horses
  3. Helping build lean muscle tissue

Product DetailsRice bran actually contains a fair amount of oil - nearly 20% oil in fact. This fat content gives the bran the calories that benefit working horses, racing horses, other performance horses and any horse that needs extra calories in their diet to increase body weight.

Stabilized Rice Bran

Experts recommend the stabilized version unless you are planning to use all the bran within a week of opening the package. This is because the product can quickly go rancid if it is not stabilized, due to the fat content.

Manufacturers stabilize this suppliment by adding mixed tocopherols (such as Vitamin E) to prevent it from going rancid.  This actually makes the rice bran more beneficial as well as helping preserve it.

In warm or humid climates stabilized product is even more important as the product will go bad faster in a moist situation.

In addition, the length of time the the dry product sits in the bag from the removal to the time it is feed can impact the nutritional value the bran gives to the horse, to the point that many horse experts find that the stabilized version of rice bran actually allows them to use less rice bran and save money. 

How Much Rice Bran to Feed Your Horse?Product Details

Rice bran contains about 1200 calories per pound, which really makes it an effective weight building feed. Pure oil has about 4000 calories/pound while RB also incorporates lower calorie components including fiber, starch, and proteins.  Most experts recommend no more than 2 pounds per day per horse of RB, but if in doubt check with your vet concerning the specific animal. 

Other Benefits of Feeding Horses Rice Bran

Not only is Rice Bran for Horses a highly palatable fat source, it also has a few other benefits:

Gamma oryzanol has been shown in studies to help repair and rebuild muscle tissue.Product Details

The feed includes a lot of fiber with the fat, so that it is less upsetting than feeding rice bran oil supplement for horses (for example) although the oil definitely has it's appropriate uses. 

Where to Buy RB for Horses?

The dry product comes in both powder and pellets.  It is available in some feed stores or over the internet from Amazon at reasonable prices ($33 for a 40 lb bag for example).  Major brands include Natural Glo, Manna Pro, Moorman's, ADM and Triple Crown and Kentucky Performance Brands.  Buying over the internet not only saves time, but may be more convenient if you live in a rural location or want to try products that are not available in your regular feed store.

Bon Vital Rice Bran Oil, 1 Gallon Bottle
Amazon Price: $31.55 $29.38 Buy Now
(price as of May 22, 2016)