I came off Burns for the same reason too.
I had my two retired greyhounds on a mix of the Burns Active (24% protein/20% fat) and the normal Burns but I had a job keeping weight on them depsite adding in frozen mince blocks (Prize Choice) every other day and adding Kronch FBO, Vit E and groomers EPO and Royal Jelly, etc. Decided that was silly and have had them on a ~26% protein/~16% fat Timberwolf food (at the moment Ocean Blue as I liked the grain free idea) as a complete with added veges and the 22%/12% fat Timberwolf Black Forest for every other day when they get some meat added - this variety has actually had the phosphorous levels altered so it is safe to chuck your own meat in.
I read the protein thread but still nervous to try the 36% protein/18% fat type (Wild n Natural) as all the stuff I read about retired racers harp on about less than 20% protein. Even racing feeds are usually only 28% protein, although greyhounds are actually one of the few breeds who actually get skinnier as they age rather than putting on weight, and do not carry much body fat!
The switch from Burns to Timberwolf had to happen quite quickly as I misgaged the length of time for ordering over Christmas (Zooplus were very good however as always), but their stools stayed nice and firm despite the rapid change over. Still need to tinker with the amounts to keep the weight right (has gone up a bit to much really!) and reduce the amount of poo - I always think if there is too much poo then they are not absorbing alot of it.
I have a 10 year old neutered male (Paddy), 7 year old speyed female (Frisby), (both my father-in-laws) a neutered 6 year old male (Ebony) and a 5 year old intact girl (Stamford - who came into season today and so is currently sulking in the utility room behind a baby gate to contain the dripping a bit!) on it and so far so good. Even the fussy 10 year old is gobbling it down.
My only concern now is Ebony who depsite quistel, FBO, EPO, Royal Jelly still has the bald bum and thinning coat and scurf he developed a few months back - greyhounds do have something called bald thigh syndrome but he had such a great load of hair and won BIS at a companion dog club show in the summer. His thyroid is fine, but he is still moulting a lot and greyhounds don't moult! Currently trying Bob Grass skincure...!