I haven’t used S cerevisiae myself, but it is in a probiotic paste that my vet sells, Fibreplex by Protexin. It also has fiber and prebiotics and is for helping bunnie that have stomach trouble. I trust my vet clinic and I trust the brand protexin because they make a probiotic för dogs that I’ve used several times and which always fixes my dog (and my dog before her) right up in cases of garbage-can-tummy (I don’t let my dogs eat from garbage-cans, it’s just jokingly called that). But I haven’t used the type for bunnies. Reading about S cerevisiae I find it can kill other types of yeasts by producing toxins that aren’t harmful to humans or animals, just to other types of yeast. Perhaps, but I’m only speculating here, killing-off of other yeast species could cause a bit of tummy upset? When you start on a new probiotic you may get a little upset stomach the first few days, there’s often a warning to that effect on the pill-jars.
Malt seems rather common in supplements for rabbits, as a digestive aid. Honey of course has lots of sugar, which isn’t great for bunnies. As I understand it, anima strath is Bio-strath for animals. I’ve never used it for any animal, but my mother made us kids drink Bio-strath when I was little. I can still almost feel the horrid taste in the back of my mouth =) It’s probably a lot tastier to bunnies (after all they love lettuce that’s grown super-bitter etc).