I hjave been told by 3 different stores that hay stretcher pellet is the same make up as hay and can be feed with hay, when hay is in short supply it stretches out your ration. If you feed the pellet you can feed less hay but they do need to still receive some hay.
I had used this for some time and was perfectly happy with it BUT then read that "you don't know the quality of the hay that is going into the pellet", this made sense to me and I thought it was better to feed just good quality hay but it is suitable for horses, or so I was told by the Blue Seal food company.