Hey Daz, how ya been kiddo?
I used to tend horses in Venice at Ringling Bros. Winter Quarters in Venice and the draft horses didn't get anymore to eat than I ever fed any of my quarter horses and they stayed good and healthy on that.
Not being the resident expert here on the feed or anything, I would only say that I wouldn't be lowering it any more at this time since you have already cut it and begun to work them. Since the mares are not used to being worked at all, and now they are, I suspect they are going to be loosing weight while they are trying to build muscle and supple themselves so don't get in a rush and be careful and go slowly. Don't forget either that you may never be able to bring their bellys back up to "perfect" either after having giving birth multiple times. Remember that they have not been used to any exercise at all so watch for soreness and lameness to come on. That would just be like someone asking me to get out of my reclyner after all these years and start doing areobics. Would I be sore? You betcha. And stiff and crabby and tired too, so just go really slow on this conditioning.
I would also suggest that you weigh your feed on a weigh scale also so you can keep track in pounds what you are actually feeding and then make a chart to post in your tack room where you can keep tabs on it. A good idea for you would be to take weekly pictures of profiles to study their body changes. Like any big horse when I'm trying to figure out if the horse is getting enough or not enough to eat, I really just stand the horse up square and eyeball him real good about every week or so and evaluate often and then also stick him out on a lunge line and just watch him real close.
