I use saracen equijewel as nearly all other weight gain feeds/supplements contain soya which my boy is allergic to
I now merely feed flaked barley and equijewel - but I feed I whole scoop of ej per day - he's regained the weight he lost when he had to come off D&H build-up cubes (which I'd recommend if your boy can tolerate soya). The EJ is expensive though - 30 quid nearly for a 20 kg bag - but it does work.
