I used Alfa A lite for an old pony I once had, as a hay replacer.  I used to fill a large muck tub type bucket with it and hi fibre cubes and add water to make it mushy for him as it is so dry fed in large quantities.  He did well on it.

I used Alpha as a hay replacement last year with no problems. I also added some Allen & Page Fast Fibre to it and mixed it all in (Fast Fibre is also suitable as a hay replacement).

The FF acted as a bulking agent and allowed my 35 year old gelding to keep on (and even put on some) weight over the winter months.

go with the guidelines on the packaging and you should be fine.