It doesn't work on my mare, and she won't touch her feed with it in either! She is a cob so normally greedy! I find Stroppy Mare brilliant! It is about half the price of oestress to!
I have used oestress for a few years now, took her off it a couple of years ago just to see if it was all in my head and she was back on it within a week. There is somebody on here who is brilliant on all the supplements who told me to feed magnesium (which i already use) and something else which I can't remember, hopefully she will come on and comment on this as i was just thinking about it today. the things were what oestress is made up with minus the fillers.
I feed both my mares Oestress throughout winter (when they live in, they're both on it as they're mother and daughter....seems to have passed on the grumpy gene!). I definately see a noticeable difference when they're on it! One mare absolutely loves the stuff, she seemingly likes the smell a lot too.
i fed my mare it last summer, seemed to calm her down a little! she is very good, apart from when she is in season when she is a monster to ride!! it definately helped, i was just debating when to restart it!!