Will a ration balancer decrease my mare's hay/grass consumption?

She is an 8 y/o Belgian and Quarter cross. She is a very easy keeper. I haven't weighed her or anything recently, but she's about 13 or so hands and about 880 - 900 lbs I guess. She is built like a tank so it's not all fat. She is very food motivated. I am wondering if feeding her a ration balancer will decrease the amount of hay or pasture she eats (if it is free choice)? She has a light workload. Sometimes I don't do much of anything with her, but lately I've been riding her more often. So she's maybe ridden twice a week (usually more if my younger sister rides her). When she is ridden it's usually for about an hour sometimes more (sometimes less it just depends). She turned out 24/7, but her pen doesn't have much grass at all so during the summer I usually take her and the others out to our neighbor's field to graze. I don't like her to be over there for too long because as I said before she is a very easy keeper and tends to eat a lot. When she's left for too long she looks pretty round in the belly. Some work usually brings it down again. All that said her workload is light and she is a very easy keeper. She tends to eat a lot so I'm wondering if a ration balancer would decrease how much hay/grass she eats? Thanks in advance for any input you may have.

No. A ration balancer functions the same as an other hard feed ration would; the only difference is RB is super concentrated, so you only have to feed it in small amounts in order for it to be sometimes more nutritious than a normal grain ration twice or triple its size. Also, RB's are not usually grain based, rather they are generally made of alfalfa, rice bran, beet pulp, etc.