Questions about rice bran?

i took in a horse a month ago, and I've been feeding him beet pulp in addition to gr hay, and he just isn't gaining as much as I would've liked. he has gained some weight but not as much as I would've hoped for, so I was thinking about adding rice bran to his diet. I'm just wondering about it because I'm not sure what the difference is between the rice bran oil and isn't there a pelleted kind. which one do i use? i know i should feed about 2 lbs of it and that it should be fortified because of the Ca/K ratio. just basically, if you can tell me everything i need to know about feeding it and preparing it to be fed. thanks i really appreciate it. I'm new to supplement stuff because my other horse was a super easy keeper.