@Caol Ila have you tried the dengie meadow grass with herbs? My fussy one really liked it and there's nothing horrific in it. I moved onto Grasstatic to stretch out the Agrobs musli as it's cheaper than the dengie but he liked it.
It's a pain because you have to commit to a whole bag and hope for the best.
My old horse would eat anything (until cushings meds in her old age made her fussy). It was pretty great. These two are picky, ridiculous creatures who would live on the horsey equivalent of whisky and fish and chips given the chance. I guess they are both bred in Scotland.
On that note, someone I was talking to somewhere did suggest beer. LOL.