Rice bran has been reported (by one breeder) to be more efficient in putting on weight than any of the senior supplements.

 "Rabbit pellets are somewhat easier to chew, so I use them as part of the mix I feed those who need weight gain, along with beet pulp, rice bran, senior horse, and llama pellets. Most pellets are alfalfa based, the differences being in mineral and additive content. The rice bran does seem to make a difference."
 

     "Blue Seal makes an equine senior supplement called "sentinel senior" (used to be called "vintage senior) that works by itself without any other supplements.  It's easy to chew, even for animals with no teeth (extruded).  It's like cheese curls in texture".

 

     "Cracked corn adds calories and heat, shredded beet pulp adds calories".