Senior feed for a horse with Cushings?

We are caring for a 30-year old horse that has been recently diagnosed with early stage Cushings. We have been giving her senior feed because that is what her owner (who is very ill and cannot currently care for her) has been giving her for years along with orchard grass hay. The vet told us to double up on the feed we have been giving her because she is dropping weight. The current senior feed is a generic blend from a local feed store (their label). We are just wondering if there might be something better that still has a high calorie content. I am planning on calling the vet later this morning to ask, but I thought maybe there was someone on here who is knowledgeable on the subject as we are in unfamiliar territory.

We need to buy some today so any input is appreciated! Thanks!!

I have a 26 year old warmblood boarded with me with Cushings and he is also the underweight version (as well as suffering from anhydrosis -not sweating). Stop with the senior feed- these horses will not react well with the corn content and the sugar content in most feeds. I have this guy on Purina Wellsolve which is designed for horses with metabolic and medical issues as well as age issues. It is very expensive but between the Wellsolve, soaked alfalfa cubes and supplemented with a free choice mineral supplement (Rush Creek from Advanced Biological Concepts) and plain salt he is healthier now (and sweating!) than he was a few years ago still working. This diet supplies him with the proteins and fats as well as good digestible carbs so I am not stressed about the possibilities of laminitis or wasting. He is also on Pergolide meds.

I also have two Insulin Resistant horses (metabolic or whatever you would like to currently term it) who are on either Wellsolve or ALAM from McCauley's Feed in Kentucky. PM me if you would like some contact numbers for two nutritionists who specialize in these types of cases.